Doctoral dissertation

To be presented by permission of the Faculty of Medicine of the University of Kuopio

for public examination in Auditorium L21, Snellmania building, University of Kuopio,

on Friday 26th September 2008, at 12 noon

Department of PsychiatryUniversity of Kuopio and

Kuopio University Hospital

PÄIVI MAARANEN

Dissociation in theFinnish General Population

JOKAKUOPIO 2008

KUOPION YLIOPISTON JULKAISUJA D. LÄÄKETIEDE 439KUOPIO UNIVERSITY PUBLICATIONS D. MEDICAL SCIENCES 439

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Series Editors: Professor Esko Alhava, M.D., Ph.D. Institute of Clinical Medicine, Department of Surgery Professor Raimo Sulkava, M.D., Ph.D. School of Public Health and Clinical Nutrition Professor Markku Tammi, M.D., Ph.D. Institute of Biomedicine, Department of Anatomy

Author´s address: Department of Psychiatry Kuopio University Hospital P.O.Box 1777 FI-70211 KUOPIO Tel. +358 17 175 226 Fax +358 17 175 391

Supervisors: Professor Heimo Viinamäki, M.D., Ph.D. Department of Psychiatry University of Kuopio and Kuopio University Hospital Docent Antti Tanskanen, M.D., Ph.D. Department of Psychiatry University of Kuopio

Reviewers: Docent Hannu Lauerma, M.D., Ph.D. Department of Psychiatry University of Turku

Docent Juha Veijola, M.D., Ph.D. Department of Psychiatry University of Oulu

Opponent: Professor Simo Saarijärvi, M.D., Ph.D. Department of Psychiatry University of Turku

ISBN 978-951-27-0959-5ISBN 978-951-27-1056-0 (PDF)ISSN 1235-0303

KopijyväKuopio 2008Finland

Maaranen, Päivi. Dissociation in the Finnish general population. Kuopio University Publications D. Medical Sciences 439. 2008. 97 p. ISBN 978-951-27-0959-5 ISBN 978-951-27-1056-0 (PDF) ISSN 1235-0303

Abstract

The aim of this epidemiological study was to investigate the prevalence of psychological and somatoform dissociation and associated factors in the general population. The course of psychological dissociation was examined in a three-year follow-up study. Dissociation was measured with the Dissociative Experiences Scale (DES) and its subscale for pathological dissociation, the Dissociative Experiences Scale Taxon (DES-T), and with the Somatoform Dissociation Questionnaire (SDQ-20).

Participants in the study (n = 3004) were derived from a random sample of general population adults (25-64 years old) in eastern Finland. The data were gathered by postal questionnaires in 1998, 1999 and 2001. The response rate was 68% at baseline, and 75% of the baseline respondents returned the questionnaire on three-year follow-up in 2001.

The prevalence of pathological dissociation (DES-T 20) was 3.4% in the general population, and there was no association between pathological dissociation, gender or age. Single, divorced or widowed subjects were more often high dissociators. Frequent alcohol consumption, a poor financial situation and a reduced working ability were associated with pathological dissociation. The cross-sectional association between pathological dissociation, depression, alexithymia and suicidal ideation was estimated as strong.

The prevalence of somatoform dissociation (SDQ-20 30) was 9.4% in the general population. Unemployment, a reduced working ability and a poor financial situation were associated with high somatoform dissociation. There was a graded relationship between high somatoform dissociation and an increasing number of adverse childhood experiences (ACEs). Of the individual ACEs, childhood physical punishment was associated with high somatoform dissociation.

A decile of the sample was investigated to assess the relationship between psychological and somatoform dissociation. Those with both high psychological and high somatoform dissociation clearly differed from the other groups: they had more depressive symptoms and more frequently reported suicidal ideation, a reduced working ability, a poor financial situation, poor general health and inadequate social support than subjects in the other groups. The correlation between the DES and SDQ-20 scores was 0.60, indicating common background factors for the two domains of dissociative experiences.

In the follow-up study, of the 98 high dissociators at baseline, 28 subjects (29%) were stable high dissociators (DES 20), while among 70 subjects (71%) the DES score declined below the cut-off score. Of the healthy participants at

baseline, 28 (2%) became new high dissociators, while 1371 (92%) out of the total cohort of 1497 participants were constantly low dissociators. Dissociative taxon membership was detected in 39 subjects either at baseline or on follow-up, but only four of them met the criteria in both assessments. Stable high dissociation was associated with an increase in the BDI score on follow-up, baseline suicidal ideation, a younger age, a reduced working ability and smoking. Risk factors for becoming a new high dissociator were an increase in the BDI score, a younger age at baseline and a reduced working ability. Among the baseline high dissociators, recovery from high dissociation was associated with a decline in the BDI score on follow-up, and with no suicidal thoughts, older age and a good working ability at baseline.

This study provided new information on the prevalence and stability of dissociation and associated factors in the general population. The comorbity of dissociative symptoms should be noted among depressive and suidical patients in clinical practice.

National Library of Medicine Classification: QZ 53, WA 900, WA 950, WM 141, WM 170, WM 171, WM 173.6, WM 270

Medical subjects headings: Age Factors; Comorbidity; Cross-Sectional Studies; Demography; Depression/epidemiology; Depressive Disorder/epidemiology; Dissociative Disorders/epidemiology; Domestic Violence; Employment; Family Health; Finland/epidemiology; Follow-Up Studies; Health Status; Health Surveys; Life Change Events; Population Surveillance/methods; Prevalence; Prospective Studies; Psychiatric Status Rating Scales; Questionnaires; Risk Factors; Sex Factors; Social Support; Somatoform Disorders/epidemiology; Substance-Related Disorders/epidemiology; Suicide, Attempted/statistics & numerical data; Suicide/psychology; Work Capacity Evaluation

Maaranen, Päivi. Dissosiaatio suomalaisessa yleisväestössä. Kuopion yliopiston julkaisuja D. Lääketiede 439. 2008. 97 s. ISBN 978-951-27-0959-5 ISBN 978-951-27-1056-0 (PDF) ISSN 1235-0303

Tiivistelmä

Tämä neljästä eri osajulkaisusta koostuva väitöskirjatyö pohjautuu Kuopion yliopistollisen sairaalan psykiatrian

klinikassa toteutettuun yleisväestön mielenterveyttä kartoittavaan alueelliseen yleisväestöotokseen. Väestöotokseen valittiin satunnaisesti 25-64-vuotiaita aikuisia (n = 3004). Itse täytettävien tutkimuslomakkeiden avulla saatu tieto kerättiin postikyselynä vuosina 1998, 1999 ja 2001. Epidemiologisen tutkimuksen tavoitteena oli tutkia psykologisen ja somatoformisen dissosiaation vallitsevuutta ja niihin yhteydessä olevia tekijöitä. Psykologisen dissosiaation kulkua mitattiin lisäksi kolmen vuoden seurantatutkimuksella. Dissosiaation mittamiseen käytettiin itsetäytettäviä mittareita: Dissociative Experiences Scale (DES) - asteikkoa, siitä johdettua patologista dissosiaatiota mittaava Dissociative Experiences Scale Taxon (DES-T) - asteikkoa ja Somatoform Dissociation Questionnaire (SDQ-20) - mittaria.

DES-T-mittarilla mitattuna patologisen dissosiaation prevalenssi yleisväestössä oli 3.4%, johon iällä tai sukupuolella ei ollut merkittävää vaikutusta. Patologiseen dissosiaatioon yhteydessä olevina taustatekijöinä nousi esille alkoholinkäyttö, huono taloudellinen tilanne ja alentunut työkyky. Yksin asuvilla, eronneilla tai leskillä patologinen dissosiaatio oli yleisempää kuin parisuhteessa elävillä. Psykiatriset muuttujat, aleksitymia, depressio ja itsetuhoisuus, olivat voimakkaasti yhteydessä patologiseen dissosiaatioon poikkileikkaustutkimuksessa (osajulkaisu I).

Somatoformista dissosiaatiota mitattiin SDQ-20-mittarilla, ja sen prevalenssi yleisväestössä oli 9.4%. Somatoforminen dissosiaatio lisääntyi iän myötä ja se oli yleisempää miehillä. Siihen yhteydessä olevia tekijöitä olivat työttömyys, alentunut työkyky ja huono taloudellinen tilanne. Lapsuuden ajan haitallisilla kokemuksilla oli yhteys somatoformiseen dissosiaatioon: useamman lapsuudenaikaisen haitallisen kokemuksen yhtäaikainen esiintyminen oli yhteydessä kohonneeseen somatoformiseen dissosiaatioon ja yksittäisistä muuttujista lapsen fyysinen rankaiseminen ennusti aikuisiän kohonnutta riskiä somatoformiseen dissosiaatioon. (osajulkaisu II).

Psykologisen ja somatoformisen dissosiaation välisen suhteen tarkemmaksi tutkimiseksi väestöotoksesta poimittiin yhtä suuret ryhmät korkeimpia pisteitä saaneista henkilöistä kahdella dissosiaatiota mittaavalla asteikolla (DES ja SDQ-20). Tämä kahden dissosiaation komorbidi ryhmä havaittiin muista selvästi poikkeavaksi: heillä esiintyi merkittävästi enemmän depressio-oireita ja itsetuhoajatuksia. Lisäksi heillä oli alentunut työkyky, huono taloudellinen tilanne, huonoksi koettu terveydentila ja riittämättömästi sosiaalista tukea verrattuna muihin ryhmiin. Psykologisen ja somatoformisen dissosiaation välinen korrelaatio havaittiin sinällään merkittäväksi (osajulkaisu III).

Kolmen vuoden seurantatutkimuksessa lähtötilanteen 98:sta korkeasti dissosioivasta henkilöstä DES-mittarilla mitattu psykologinen dissosiaatio oli pysyvää vain 28 henkilöllä (29%), 70 henkilöllä (71%) DES-pisteet laskivat katkaisurajana käytetyn 20 pisteen alle. Alkuvaiheen terveistä henkilöistä (n = 1399) 28:lla henkilöllä (2%) pisteet vastaavasti nousivat katkaisurajan yli, ja pysyvästi matalat DES-pisteet oli koko seurannan ajan 1371 henkilöllä (92%). Pysyvä korkea dissosiaatio oli yhteydessä BDI-pisteiden lisääntymiseen seuranta-aikana, itsetuhoisuuteen, nuoreen ikään, alentuneeseen työkykyyn ja tupakointiin. DES-Taxon-mittarin avulla laskettuun patologisesti dissosioivien luokkaan kuului koko tutkimuksessa 39 henkilöä, mutta vain neljällä henkilöllä tämä ominaisuus oli pysyvä. Tämän tutkimuksen perusteella DES-Taxon luokkaan kuuluminen eri mittausajankohdissa ei kuvannut pysyvää ilmiötä.

Tässä tutkimuksessa saatiin uutta tietoa dissosiaation vallitsevuudesta ja pysyvyydestä sekä niihin liittyvistä tekijöistä suomalaisessa yleisväestössä. Dissosiaatio-oireiden tunnistaminen komorbidien depressio-oireiden ja itsemurha-ajatusten yhteydessä tulisi ottaa huomioon myös kliinisessä työssä.

Yleinen suomalainen asiasanasto: dissosiaatiohäiriö; epidemiologia; kyselytutkimus; mielenterveys; mielenterveyshäiriöt; suomalaiset; tunne-elämän häiriöt

To my family

Acknowledgements

This thesis is based on a longitudinal project, the Kuopio Depression (KUDEP) study, carried

out at the Department of Psychiatry, Kuopio University Hospital between 1998 and 2001. I want to

express my gratitude to all the participants in the general population survey. Without their

collaboration, this study would not have been possible or successfully accomplished.

I wish to express my sincere gratitude to my principal supervisor, Professor Heimo Viinamäki,

who has provided the facilities to perform this study. His tireless optimism, enthusiastic guidance

and practical knowledge of writing scientific articles have provided support in carrying out all

phases of my thesis.

I owe my deepest gratitude to my supervisor, Docent Antti Tanskanen, who proposed the topic

of this thesis to me and introduced me to the world of scientific research. His pioneering work on

dissociation and psychic traumatization made it possible to perform this thesis as part of the

KUDEP project. It has been a privilige to work under his expert, intelligent and encouraging

guidance. He has always been able to arrange time for appointments and discussions, even during

the last few years after he moved to Helsinki.

I am grateful to the official reviewers of the thesis, Docent Hannu Lauerma and Docent Juha

Veijola, for their valuable suggestions and advice for the improvement of this thesis.

I am very grateful to my co-authors, head nurse Kaisa Haatainen, Professor Jukka Hintikka,

Docent Kirsi Honkalampi, and Professor Heli-Koivumaa-Honkanen. They each have helped me

during this study: in scientific writing, statistical issues and giving valuable opinions from other

aspects of this project.

For statistical advice I am thankful to Vesa Kiviniemi and Marja-Leena Hannila from the Center

of Statistical and Mathematical Services at the University of Kuopio. I wish to thank Roy Siddall

for his excellent work in revising the English manuscripts. I thank secretary Eeva-Maija Oittinen for

her friendly advice and practical help with the preparation of this thesis.

I wish to thank all my friends and colleagues in the Department of Psychiatry, Kuopio University

Hospital, for collaboration and support during the process of completing this thesis. I warmly thank

my secretary Sari Alismaa for being next door to my office and providing endless good humor and

secreterial advice during the last phases of my work. I am especially grateful to retired head

physician Juha Jääskeläinen for his encouragement to begin my scientific work, and Docent Pirjo

Saarinen for her support as the head physician during the process of preparing this thesis. I am

grateful to Professor Johannes Lehtonen for the facilities to carry out the work in this thesis and for

his interest in my scientific work on dissociation.

It has been a great opportunity for me to be part of a two-year education program by

Traumaterapiakeskus in Helsinki in 2006-2008. This education program introduced the participants

to the Theory of Structural Dissociation and phase-oriented treatment of complex trauma-related

disorders. This education has been invaluable to me in understanding trauma and dissociation, and

learning diagnostic tools as well as psychotherapeutic treatment methods for dissociative disorders.

I wish to express my sincere gratitude to Anne Suokas-Cunliffe for organizing this education

project and to all my teachers: Suzette Boon, Ellert Nijenhuis, Kathy Steele, and Onno van der Hart.

I am very grateful to my dear friends Hannele and Maarit for being there for me. We have been

friends since the beginning of our medical studies, and shared countless things in our personal and

professional life during the university years and after that together.

I warmly thank my parents, Mirja and Aimo Hujanen, for their love and support. They have

always encouraged me to learn and study. Their help in countless practical things has been

invaluable to me during this process. To my brother Pasi and his wife Minna and their children

Roosa and Roope, many thanks for sharing many happy moments together. Finally, I wish to

express my deepest gratitude to my husband Aki and to my children Iida and Akseli for all that love

and happiness you have brought me. Special thanks to Iida for discussions about writing and also

for helping me arrange the references.

Kuopio, August 2008

Päivi Maaranen

Abbreviations

ACE Adverse Childhood Experience

A-DES The Adolescent Dissociative Experiences Scale

ANP Apparently Normal part of the Personality

APA American Psychiatric Association

BDI Beck Depression Inventory

CI Confidence interval

DD Dissociative Disorder

DES Dissociative Experiences Scale

DES-ABS Absorption and imaginative involvement factor of the Dissociative

Experiences Scale

DES-AMN Amnestic factor of the Dissociative Experiences Scale

DES-DD Depersonalization-derealization factor of the Dissociative Experiences

Scale

DES-NP Non-pathological dissociation

DES-T Subscale of the Dissociative Experiences Scale measuring pathological

dissociation (DES-Taxon)

DID Dissociative Identity Disorder

DIS-Q Dissociation Questionnaire

DSM Diagnostic and Statistical Manual of Mental disorders

EP Emotional part of the Personality

ICD International Classification of Diseases and Related Health Problems

OR Odds Ratio

PTSD Post-traumatic Stress Disorder

SCID-D Structured Clinical Interview for Dissociative Disorders

SD Standard Deviation

SDQ-20 Somatoform Dissociation Questionnaire

SDQ-5 Screening version of the Somatoform Dissociation Questionnaire

SPSS Statistical Package for the Social Sciences

TAS-20 The Toronto Alexithymia Scale

List of original publications

Original publications are referred to in the text by the Roman numerals I-IV.

I Maaranen P., Tanskanen A., Honkalampi K., Haatainen K., Hintikka J., Viinamäki H.

Factors associated with pathological dissociation in the general population. Australian

and New Zealand Journal of Psychiatry 2005; 39:387-394.

II Maaranen P., Tanskanen A., Haatainen K., Koivumaa-Honkanen H., Hintikka J.,

Viinamäki H. Somatoform dissociation and adverse childhood experiences in the

general population. Journal of Nervous and Mental Disease 2004; 192:337-342.

III Maaranen P., Tanskanen A., Haatainen K., Honkalampi K., Koivumaa-Honkanen H.,

Hintikka J., Viinamäki H. The relationship between psychological and somatoform

dissociation in the general population. Journal of Nervous and Mental Disease 2005;

193:690-692.

IV Maaranen P., Tanskanen A., Hintikka J., Haatainen K., Honkalampi K., Koivumaa-

Honkanen H., Viinamäki H. The course of dissociation: a 3-year follow-up study.

Comprehensive Psychiatry 2008; 49:269-274.

The original papers have been reproduced with the permission of the publishes.

CONTENTS 1. INTRODUCTION ...................................................................................................................................................... 19

2. REVIEW OF THE LITERATURE .......................................................................................................................... 20

2.1. HISTORY ............................................................................................................................................................... 202.1.1. Hypnosis ....................................................................................................................................................... 222.1.2. Towards the 21st century .............................................................................................................................. 23

2.2. DEFINITIONS OF DISSOCIATION ........................................................................................................................... 242.2.1. Dissociation as a defence mechanism ......................................................................................................... 252.2.2. Cognitive theory............................................................................................................................................ 262.2.3. Dissociation as a symptom ........................................................................................................................... 27

2.2.3.1. Psychological dissociative symptoms .....................................................................................................................272.2.3.2. Somatoform dissociative symptoms.......................................................................................................................282.2.3.3. Dissociative symptoms according to the Structural Dissociation Theory...........................................................29

2.2.4. Dimensional or categorical construct? ........................................................................................................ 312.2.5. Dissociation as a disorder and the classification of dissociative disorders................................................. 33

2.3. BIOLOGICAL FACTORS IN DISSOCIATIVE PATHOLOGY........................................................................................ 362.4. ASSESSMENT OF DISSOCIATIVE SYMPTOMS WITH QUESTIONNAIRES ................................................................. 37

2.4.1. The Dissociative Experiences Scale (DES) ................................................................................................. 372.4.2. The Somatoform Dissociation Questionnaire (SDQ-20) ............................................................................ 382.4.3. Other measures............................................................................................................................................. 39

2.4.3.1. The Dissociation Questionnaire (DIS-Q)...............................................................................................................392.4.3.2. The Adolescent Dissociative Experiences Scale (A-DES) ....................................................................................402.4.3.3. The Multidimensional Inventory of dissociation (MID) ......................................................................................40

2.5. DISSOCIATION IN THE GENERAL AND NON-CLINICAL POPULATION ................................................................... 402.5.1. Prevalence of dissociative symptoms in general and non-clinical populations.......................................... 40

2.5.1.1. Prevalence of psychological dissociation ...............................................................................................................402.5.1.2 Prevalence of somatoform dissociation ..................................................................................................................41

2.5.2. Factors associated with dissociation............................................................................................................ 432.5.2.1. Sociodemographic factors ......................................................................................................................................43

2.5.2.1.1. Age ...................................................................................................................................................................432.5.2.1.2. Sex....................................................................................................................................................................432.5.2.1.3. Sosioeconomic and marital status.....................................................................................................................43

2.5.2.2. Adverse Childhood Experiences ............................................................................................................................442.5.2.3. Other psychiatric conditions ..................................................................................................................................45

2.5.2.3.1. Depression and suicidality ................................................................................................................................452.5.2.3.2. Other psychiatric disorders ...............................................................................................................................46

2.5.2.4. Alexithymia .............................................................................................................................................................472.5.2.5. Substance use (alcohol and tobacco)......................................................................................................................492.5.2.6. Familiality................................................................................................................................................................49

2.5.3. The relationship between psychological and somatoform dissociation ...................................................... 502.5.4. Stability of dissociative symptoms ................................................................................................................ 50

3. AIMS OF THE STUDY ............................................................................................................................................. 52

4. PARTICIPANTS AND METHODS ......................................................................................................................... 53

4.1. STUDY DESIGN ...................................................................................................................................................... 534.2. STUDY POPULATION ............................................................................................................................................. 54

4.2.1. Study I........................................................................................................................................................... 544.2.2. Study II ......................................................................................................................................................... 554.2.3. Study III........................................................................................................................................................ 554.2.4. Study IV ........................................................................................................................................................ 55

4.3. METHODS.............................................................................................................................................................. 564.3.1. The assessment of dissociation .................................................................................................................... 56

4.3.1.1. The Dissociative Experiences Scale (DES) ............................................................................................................574.3.1.2. The Somatoform Dissociation Questionnaire (SDQ-20) ......................................................................................57

4.3.2. Depression .................................................................................................................................................... 584.3.3. Suicidal ideation ........................................................................................................................................... 584.3.4. Alexithymia................................................................................................................................................... 594.3.5. Adverse childhood experiences (ACEs) ....................................................................................................... 594.3.6. Statistical analysis ........................................................................................................................................ 60

5. RESULTS.................................................................................................................................................................... 62

5.1. PATHOLOGICAL DISSOCIATION (STUDY I)........................................................................................................... 625.1.1. The prevalence of pathological dissociation and mean scores of the DES in the general population...... 625.1.2. Factors associated with pathological dissociation....................................................................................... 62

5.2. SOMATOFORM DISSOCIATION (STUDY II) ........................................................................................................... 635.2.1. The prevalence of somatoform dissociation and the mean scores of the SDQ-20 in the general population................................................................................................................................................................................ 635.2.2. Sociodemographic variables ........................................................................................................................ 635.2.3. Adverse childhood experiences (ACEs) ....................................................................................................... 63

5.3. THE RELATIONSHIP BETWEEN PSYCHOLOGICAL AND SOMATOFORM DISSOCIATION (STUDY III).................... 645.4. COURSE OF DISSOCIATION IN THE GENERAL POPULATION (STUDY IV) ............................................................. 65

5.4.1. Stability of psychological dissociative symptoms......................................................................................... 655.4.2. Associations between dissociation, depressive symptoms and suicidal ideation ........................................ 65

6. DISCUSSION.............................................................................................................................................................. 67

6.1. PREVALENCE OF DISSOCIATION IN THE GENERAL POPULATION ........................................................................ 676.2. FACTORS ASSOCIATED WITH DISSOCIATION ....................................................................................................... 68

6.2.1. Age ................................................................................................................................................................ 686.2.2. Sex................................................................................................................................................................. 696.2.3. Socioeconomic and marital status ............................................................................................................... 696.2.4. Substance use (alcohol and tobacco)........................................................................................................... 70

6.3. COMORBIDITY BETWEEN DISSOCIATION, DEPRESSIVE SYMPTOMS AND SUICIDAL IDEATION ........................... 706.3.1. Comorbidity between dissociative experiences and depressive symptoms .................................................. 716.3.2 The relationship between psychological and somatoform dissociation ....................................................... 736.3.3. The relationship between dissociation and suicidal ideation...................................................................... 73

6.4. THE RELATIONSHIP BETWEEN DISSOCIATION AND ALEXITHYMIA ..................................................................... 746.5. THE IMPACT OF ADVERSE CHILDHOOD EXPERIENCES (ACES) ON SOMATOFORM DISSOCIATION .................... 766.6. THE STABILITY OF DISSOCIATIVE SYMPTOMS ..................................................................................................... 776.7. A CATEGORICAL OR DIMENSIONAL CONSTRUCT?............................................................................................... 786.8. METHODOLOGICAL CONSIDERATIONS ................................................................................................................ 79

6.8.1. Study population and design ........................................................................................................................ 796.8.2. The Dissociative Experiences Scale and Somatoform Dissociation Questionnaire................................... 806.8.3. Other measures............................................................................................................................................. 81

7. CONCLUSIONS......................................................................................................................................................... 82

7.1. CONCLUSIONS FROM THE RESULTS ..................................................................................................................... 827.2. SUGGESTIONS FOR FUTURE RESEARCH................................................................................................................ 827.3. CLINICAL IMPLICATIONS ..................................................................................................................................... 83

REFERENCES ............................................................................................................................................................... 84

Tables

Table 1. The phenomenological categorization of dissociative symptoms (Van der Hart et al.,

2006).

Table 2. A synopsis of the classification of dissociative disorders with comparisons between

the ICD-10 and DSM-IV-TR.

Table 3. Prevalence of high dissociation and mean scores from questionnaires on dissociation

in non-clinical population samples.

Table 4. The relationship between dissociation and alexithymia in clinical and non-clinical

samples.

Table 5. Sociodemographic characteristics of the subjects in studies I-IV.

Figure

Figure 1. Formation of the study population.

Appendices

Appendix I Dissociative Experiences Scale

Appendix II Somatoform Dissociation Questionnaire

19

1. Introduction

In the past two decades, the debate over dissociation and dissociative disorders has been

accompanied by an increase in the number of studies and articles on dissociation. This surge

follows a long history of clinicians and researchers simply seeking to evidence the existence of

dissociative phenomena. Early endeavours to document dissociative phenomena were often based

on case study descriptions and philosophical musings (Rieber, 2002). Many of the ideas of the early

theorists who grappled with dissociative phenomena are quite relevant today.

As the concept of dissociation has gained traction in mainstream psychology and psychiatry in

recent years, empirical investigation has enhanced our understanding of the complexity of

dissociative phenomena. Definitional issues are of central importance to both theory building and

empirical investigation. As the field grows, delineating and clarifying definitional issues, such as

whether dissociation is premised to be a state or trait, a continuum or a taxon, or some combination,

is of critical importance. Theory building, assessments and data interpretation all inherently depend

on answers to these questions (DePrince and Cromer, 2006). Our studies on dissociation in the

general population provide some answers to these issues.

Somatoform dissociation has gained significance in research on dissociation through the work of

Ellert Nijenhuis and his Dutch colleagues. They have described the phenomenology of somatoform

dissociation and its relationship with various traumatic experiences. They have constructed

psychometrically sound instruments for measurement and have developed an important theoretical

perspective (Nijenhuis, 2000; Nijenhuis et al., 1996, 1998a, 1999). The categorization of conversion

and dissociative disorders in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV),

and whether they should be placed in the same category of dissociative disorders, is being evaluated

in the development of DSM-V. However, epidemiological studies in the general population on

somatoform dissociation or on the relationship between psychological and somatoform dissociation

have been lacking.

20

2. Review of the literature

2.1. History

Known from Pharaonic Egypt and Greece, hysteria had been considered a disease of somatic

nature and origin. ‘Hysteria’ is derived from the Greek word ‘hystera’, which means ‘uterus’, and

hysteria has traditionally been identified as a disease of women. The Greek theories about hysteria

were influenced by the Egyptian wandering womb hypothesis. Hippocrates (460-370 B.C.) located

mental disorders in the brain, but he thought that hysteria was a disorder of uterine origin. The

Greeks blamed celibacy for causing the womb to become lighter so that it would ascend into the

abdomen. Various suggestions for treatment included bandaging below the hypocondrium to

prevent further upward wandering, and marrying in order to become pregnant (Fink, 1996).

In the Medieval era, many illnesses and cures were attributed to sorcery, witchcraft and saints,

and little distinction was made between medical, neurological and psychological disorders. Social

attitudes toward hysteria changed; the preoccupation with demonology and witchcraft altered

societal perceptions of a hysteric from that of a sick human being to that of someone who was

deliberately possessed by the devil (Fink, 1996). With the rise of Christianity, organic theories of

hysteria were replaced by supernatural explanations and unusual female complaints were seen to be

the work of the devil (Acocella, 1999). Such beliefs led to the infamous Witch Trials, and the fate

of hysterics was similar to that of the organically ill.

Neuroanatomist Thomas Willis (1622-1675) rejected the uterine theory and proposed that the

brain and the spinal cord were the sites of the disease. However, the mind or the mental processes

were not believed necessarily to be located in the brain (Fink, 1996). Thomas Sydenham (1624-

1689) recognized hysteria as a mental disorder. This, combined with Briquet’s (1796-1881)

observation of psychological disturbances in hysteria, set the stage for the conceptualization of

hysteria as a mental disease. Jean-Martin Charcot (1825-1893) recognized that hysteria essentially

involved disturbances of perception and control. Charcot thought that “dynamic or functional

lesions” induced by emotional causes were responsible for these kinds of symptoms (Nijenhuis,

2004). Many other 19th century clinicians in Europe and the United States were confronted by

“hysterical” manifestations that severely tried their sense of what is mental and what is physical,

normal and abnormal. Many founders of modern psychopathology and psychotherapy, including

Jean-Martin Charcot, Alfred Binet and Pierre Janet, among others in France, Josef Breuer and

Sigmund Freud in Austria, and Morton Prince and William James in the United States, studied and

treated patients who presented striking, sometimes shocking, conditions. Some of these symptoms

21

(e.g. blindness, seizures) resembled those of severe somatic pathology, but were not associated with

any detectable anatomical or physiological damage. Other symptoms (e.g. amnesia, different

identities within the same individual) manifested serious cognitive deficits, again without any

medical explanation (Cardeña and Nijenhuis, 2000).

Pierre Janet (1849-1947) was the first to introduce the concept and the name dissociation

(desaggregation mentale) and its connections with traumatic aetiology. The English term merely

implies separation, whereas the French term indicated a forced separation of elements that would

normally aggregate. Janet was a pupil of Charcot and worked in the Salpêtrière clinic in France.

Janet initially elaborated the concept of dissociation in his work on psychological automatism (Van

der Hart and Friedman, 1989). He dealt with psychological phenomena often observable in hysteria,

hypnosis, states of suggestion or possession. Janet postulated that dissociation results from what he

termed la misère psychologique - that is, a pathological, presumably genetic poverty or deficiency

of basic mental energy that enables healthy persons to combine the various mental functions

(sensations, memories, volitions) into a stable, unified psychological structure under the conscious

domination and control of the personal self or ego. If, either spontaneously or as a result of the

emotional expenditure of mental energy in the face of psychological trauma, the quantum of energy

is lowered below a critical point, the binding power of the personal self is seriously impaired, and

the various psychological functions escape from its control (that is, they are dissociated, with all the

potential pathological consequences). Psychological systems that fail to integrate with the larger

personality become self-organized into a smaller and generally more rudimentary part of the

personality, which as well as having its own sense of self, can exert influence over the individual’s

behaviour (Dorahy and Van der Hart, 2006; Van der Hart and Friedman, 1989; Van der Hart and

Horst, 1989).

After the sudden death of Charcot, many of his ideas of about the presumably physical nature of

hypnosis were discarded in favour of the view that hypnosis was a psychological phenomenon

based purely on suggestion. Janet was soon the only one in the Salpêtriere using hypnosis in his

research and clinical work, and published many studies on hysteria. Babinski (1857-1932), formerly

loyal to Charcot, began to regard hysteria as essentially the result of suggestion, and even a form of

malingering; a disorder able to disappear entirely by the influence of persuasion. Dejerine (1849-

1917), the next director of the Salpêtriere clinic, regarded hypnosis as morally reprehensible, and

eventually Janet had to leave the Salpêtriere. After that he lectured in North and South America and

received an honorary doctorate at Harvard in 1936 (Van der Hart and Friedman, 1989).

22

Sigmund Freud (1856-1939), like Janet, based his initial psychological explanation of the

aetiology of hysteria on the occurrence of a dissociative disappearance from the consciousness of

mental contents that, although now unconscious, can influence the form and distribution of

hysterical symptoms. He began to regard somatoform dissociative symptoms as a result of a process

of conversion (i.e. the transformation of unacceptable mental contents into a somatic symptom).

Impressed by the painful quality of traumatic memories, he postulated that the traumatized person

actively dissociated or, in his terminology, “repressed” the painful memories from the conscious

awareness and, by a continuation of this repression, maintained them over time in an unconscious

state to prevent the conscious experiencing of the painful emotions associated with them, and by

converting the painful affects into somatic symptoms symbolically representing the precipitating

trauma (Breuer and Freud, 1955). In other words, whereas Janet adhered to the deficit model of

psychic functioning in which the ego is too weak to maintain its functional integrity, Freud

proposed a conflict model in which a strong ego preserves its normal functions and its emotional

equanimity by protecting itself from psychological pain through the operation of the defensive

mechanism of repression (Nemiah, 2000).

2.1.1. Hypnosis

The use of hypnosis was common among most clinicians studying hysteric manifestations in the

19th century, both as a means of investigation and treatment, and in France the concept of

dissociation became linked with hysteria and hypnosis. The psychological phenomena it referred to

were well known to “magnetizers” by the end of the 18th century and the beginning of the 19th

century. They observed patients who talked about themselves in the third person while in a state of

induced or artificial somnambulism, as deep hypnosis was then known (Van der Hart and Horst,

1989). One of the early magnetizers, Marquis de Puységur, began to refer to hypnotic states as

artificial somnambulism, because of their resemblance to natural sleepwalking. The word

“somnambulism” was expanded to include any kind of activity pursued while in a dissociated

condition. Hypnosis was “artificial somnambulism”, dissociation induced by a therapist for

experimental or therapeutic purposes, a deliberate imitation of hysteria. Multiple personality was a

somnambulistic condition in which two or more dissociated states are strikingly distinct in

behaviour, mood and intention, and in which one or several of the states are amnesic for one or for

others. Pierre Janet was the first to describe somnambulism as a phenomenon whereby two or more

states of consciousness are dissociated by the cleft of amnesia and seem to operate independently of

one another (Haule, 1986). Patients suffering from the 19th century diagnosis of hysteria were, as a

23

rule, highly “suggestible”. In more recent studies, associations between hypnotizability and

dissociative experiences or disorders have been found (A argün et al., 1998; Carlson and Putnam,

1989; Frischholz et al., 1992).

2.1.2. Towards the 21st century

Regardless of the differences between their theoretical models of psychological functioning, both

Freud and Janet initially emphasized the importance of traumatic events and their painful memory

traces as a central factor in the formation of dissociative symptoms. Freud later abandoned the

trauma aetiology of dissociation and shifted his attention from painful memories of actual traumatic

events to the existence of painful, developmentally-derived inner sexual and hostile drives and

fantasies as the source of psychological conflict (Blizard, 2003).

Later, the British psychologist and psychiatrist Charles Myers, with his work on World War I

soldiers, introduced the concept of psychic traumatization in war (Myers 1916a, b). He described a

basic form of structural dissociation in acutely traumatized (“shell-shocked”) World War I combat

soldiers (Van der Hart et al., 2000). Myers demonstrated that dissociation involved the co-existence

of and alternations between a so-called Apparently Normal (ANP) and an Emotional

Part (EP) of the personality. Survivors, as ANP, were fixated in trying to go on with normal life,

and were thus directed by action systems of daily life, while avoiding the traumatic memories. As

EP, they were in the action system (e.g. defence) or subsystems (e.g. hypervigilance, flight, fight)

that were activated at the time of the traumatization. This theory and the work of Pierre Janet

formed the basis of a modern dissociation theory: the Theory of Structural Dissociation (Van der

Hart et al., 2006).

Interest in dissociation and psychic traumatization began to emerge again with studies on

Vietnam War veterans and the recognition of post-traumatic stress disorder (PTSD). At the same

time, in the 1970s and 1980s, the association between dissociative disorders and childhood physical

or sexual abuse became an important issue in the study of dissociation. Ernest R. Hilgard continued

Pierre Janet’s work and tradition. In the “neodissociation” theory, Hilgard postulated that the

secondary dissociated consciousness is characterized by the hidden observer, which has the quality

of a central stream of consciousness in which information converges from many secondary streams

or secondary personalities (Hilgard, 1974, 1984).

In Finland, psychiatrist Reima Kampman was one of the pioneers in the study of hypnosis and

dissociation in the 1970s. He published his doctoral dissociation on hypnotically induced multiple

24

personality (Kampman, 1973), but consided today the weight of evidence of his work was

moderate.

Today, the importance of childhood physical and sexual abuse (Chu and Dill, 1990; Van der

Kolk et al., 1996), family dysfunction (Draijer and Langeland, 1999), parental verbal aggression

and especially multiple forms of childhood maltreatment (Teicher et al., 2006) in the development

of dissociative symptoms or disorders has been recognized and accepted. However, there still exists

much debate, especially in the United States, on the validity of traumatic memories, and on

dissociative amnesia for the traumatic memories (Chu and Bowman, 2000; Chu et al., 1999;

McNally, 2007; McNally et al., 2005). In 1992 the False Memory Syndrome Foundation was

founded. This group stated that a substantial number of professionals and therapists in the field

were utilizing suggestive and unproven techniques that resulted in vulerable patients developing

false memories of childhood abuse (Chu and Bowman, 2000). Today, the development of new

models and theories of traumatization and dissociation include more sophisticated evaluations of

reports of abuse, better differential diagnosis, and treatment focused on helping patients form a

credible sense of their personal history rather than simply uncovering more trauma (Chu and

Bowman, 2000). In recent years, individual reactions to trauma due to war and terrorist attacks have

again become a target for research.

2.2. Definitions of dissociation

A wide range of definitions for dissociation have been proposed by researchers and clinicians.

While they might differ in detail, what is common in all definitions is a reference to the lack of

usually expected connections between mental content. Dissociative experiences are characterized

by a compartmentalization of consciousness. That is, certain mental events that would ordinarily be

expected to be processed together (e.g. thoughts, emotions, motor activity, sensations, memories

and sense of identity) are functionally isolated from one another and, in some cases, rendered

inaccessible to consciousness and/or voluntary recall (Steinberg, 1994).

According to the Diagnostic Manual for Mental Disorders, Fourth edition, Text Revision (APA,

2000), the essential feature of dissociation is “a disruption of the normal integrative functions of

consciousness, memory, identity, and perception of the environment.” Nemiah (1991) defines

dissociation as “the exclusion from consciousness and the inaccessibility of voluntary recall of

mental events, singly or in clusters, of varying degrees of complexity, such as memories, sensations,

feelings, fantasies and attitudes.”

25

Somatoform dissociation denotes phenomena that are manifestations of a lack of integration of

somatoform experiences, reactions, and functions (Nijenhuis et al., 1996). Both descriptors,

psychological dissociation and somatoform dissociation, refer to the ways in which dissociative

symptoms may be manifested, not to their presumed cause. Somatoform dissociation designates

dissociative symptoms that phenomenologically involve the body, and psychological dissociative

symptoms are those that phenomenologically involve psychological variables. The descriptor

‘somatoform’ indicates that the physical symptoms resemble, but cannot be explained by, a medical

symptom or the direct effects of a substance (Nijenhuis, 2000). Psychological dissociation has also

been defined by the term psychoform dissociation (Van der Hart et al., 2006).

Definitions of dissociation also differ according to whether states or traits are being discussed.

The notion of a dissociative state implies that dissociation can be an episodic phenomenon. State

dissociation is experienced by some people some of the time, is time limited and presumably

situation triggered. A dissociative trait refers to dissociation as a common personality feature which,

like all personality features, is expressed to a greater or lesser degree in each individual (Nijenhuis,

2004).

Dissociation can be understood as a psychic defence mechanism, or as a symptom (or a cluster of

symptoms) significantly manifested in various psychiatric disorders or as a distinct disorder.

2.2.1. Dissociation as a defence mechanism

One of the main strivings of the human psychological system is to maintain organisation and

avoid disintegration. Defences are those mental and behavioural activities that protect the system

from threats to this organisation such as overwhelming, conflicting and intolerable emotions.

Simply stated, the purpose of a defence is to protect individuals by helping them to avoid or manage

these threats (McWilliams, 1994).

Central to the concept of the adaptive function(s) of dissociation is the idea that dissociative

phenomena exist on a continuum and become maladaptive only when they exceed certain limits in

intensity or frequency, or occur in an inappropriate context. Dissociation provides a capacity to

adaptively detach from disturbing emotional states, the milder manifestations being common and

highly functional, and more severe variants less common and typically less functional (Bowins,

2004). Dissociation is seen as a normal process that is initially used defensively by an individual to

handle traumatic and overwhelming experiences, and dissociative experiences are found to be risk

factors for dissociative pathology (Putnam, 1989). At the ‘normal’ end of the continuum are

commonly reported, transient and non-disruptive dissociative experiences such as becoming

26

absorbed in an activity, day-dreaming and performing well-learned actions without conscious

awareness. At the pathological end of the continuum are rarer but more pervasive and life-

disrupting experiences such as chronic depersonalization and identity alteration (Putnam, 1989).

There is a difference between dissociation, the psychodynamic notion of repression and the

conscious act of suppression. Repression refers to the sequestering of unacceptable, conflicting or

intolerable material from consciousness. Repressed psychic material cannot make itself known

directly; its existence is inferred through slips of the tongue, dreams and other symbolic

phenomena. The difference between repression and dissociation can be seen in Hilgard’s (1974)

image of repressed material as existing below a horizontal barrier, above which lies consciousness,

and dissociated material as being separated from consciousness by vertical barriers. Suppression

can be distinguished from both repression and dissociation in that it involves a conscious effort to

‘not think about’ something. The person engaged in suppression does not have amnesia for the

suppressed material, the material does not reside sub- or unconsciously and the suppressed material

can be readily accessed.

It has been suggested that trauma-induced dissociative reactions resemble the defensive reactions

of animals (freezing, aggression) (Nijenhuis et al., 1998b). Nijenhuis and coworkers have proposed

that as a result of an evolutionary mechanism common to many species, there may be a similarity

between distinct animal defensive reaction patterns and certain somatoform dissociative symptoms

of traumatized dissociative disorder patients, such as analgesia, anaesthesia and motor inhibitions

(Nijenhuis, 2004). It has been suggested that among a wide range of potentially traumatizing events,

somatoform dissociative symptoms would most strongly be associated with a bodily threat and a

threat to the life of an individual (Nijenhuis et al., 2001, 2004; Waller et al., 2000).

2.2.2. Cognitive theory

Cognitive theory proposes a cognitive organization that operates during times of perceived or

actual threat from an internal and/or external source in individuals with dissociative pathology. This

is called a dissociative processing style, which serves as a threat-monitoring system (Dorahy, 2006).

Whilst activation of the dissociative processing style has the potential for adaptive and protective

functions, it also heightens the likelihood of experiencing dissociative symptoms and dissociation

itself. It is characterized by a shift from selective attention processing to multiple streams of

information processing, weakened cognitive inhibitory functioning that allows these streams to be

operational and the directing of awareness towards some and away from other information streams.

Dissociation is understood here as a failure to integrate encoded representations (e.g. environmental

27

stimuli) and internal features (e.g. affects, cognitions) from multiple input streams that, without the

process of dissociation, would be put together (Dorahy, 2006). The findings of DePrince and Freyd

(2004) have also suggested that in an effort to avoid threat stimuli, divided attention may serve a

protective function by reducing the likelihood that such stimuli are encoded. Somewhat

controversial suggestions have also been proposed: nonpathological dissociation might reflect a

constitutionally determined cognitive style rather than a pathological trait acquired through the

experience of adverse life events (De Ruiter et al., 2006). In behavioural and neural studies, highly

dissociative individuals were characterized by heightened levels of attention, working memory and

episodic memory. Nevertheless, the authors suggest that individuals with high dissociative abilities

might be prone to develop dissociative disorders when exposed to traumatic experiences,

whereas individuals without dissociative tendencies might develop depressive symptoms, PTSD,

borderline personality or psychotic features (De Ruiter et al., 2006).

2.2.3. Dissociation as a symptom

Dissociative symptoms can be categorized in many ways. In the current scientific literature they

are divided into psychological (or psychoform) and somatoform dissociative symptoms. Core

psychological dissociative symptoms include amnesia, depersonalization, derealization, identity

confusion and identity fragmentation (Bernstein and Putnam, 1986; Steinberg, 1994). The

somatoform dissociative symptoms include a mixture of conversion and somatoform symptoms

(Nijenhuis et al., 1999).

2.2.3.1. Psychological dissociative symptoms

Dissociative amnesia is “the absence from memory of a specific and significant period of time”

(Steinberg, 1994). It is viewed as a functional amnesia as it occurs in the absence of any known

organic cause and is distinguished from other forms of amnesia such as childhood amnesia in that it

does not reflect normal psychological development. Individuals experiencing dissociative amnesia

typically retain the ability to learn and recall new information; memory loss is restricted to a

circumscribed period of time or category of events within the individual’s life, usually of a

traumatic or stressful nature (APA, 2000). Amnesia may be reversible (Bremner et al., 1996; Van

der Hart et al., 2005).

28

Depersonalization refers to a feeling of detachment or estrangement from one’s self and

includes “a sensation of being an outside observer of one’s body” and “feeling like an automaton or

as if one is living in a dream” (APA, 1994). In clinical samples, chronic depersonalisation is the

third most frequently reported symptom after depression and anxiety (Gershuny and Thayer, 1999).

Derealization refers to “an alteration in the perception of one’s surroundings so that a sense of

reality of the external world is lost” (APA, 1994). Individuals experiencing derealization may feel

as though they have lost contact with external reality; that their home, workplace, friends or

relatives are unfamiliar or strange (Steinberg et al., 1993). Transient states of

depersonalisation and derealization are common and spontaneous, especially under conditions of

fatigue, anxiety and danger (Butler et al., 1996).

Identity confusion refers to the subjective feelings of uncertainty or conflict regarding one’s

personal identity. Individuals with dissociative symptoms often express confusion as to who they

really are. They experience conflicting wishes and opinions (Steinberg et al., 1993).

In identity alteration, different ‘identities’ or ‘personality states’ take over the control of the

personality. This is also the core diagnostic feature of dissociative identity disorder (DID), where

dissociative parts of the personality (at least two alter personalities or personality states) can be

detected, and switching observed (APA, 1994). The alter personality has been defined as “an entity

with a firm, persistent, and well-founded sense of self and a characteristic and consistent pattern of

behaviour and feelings in response to given stimuli. It must have a range of functions, a range of

emotional responses, and a significant life history (of its own existence)” (Kluft, 1984).

Alternatively, the DSM-IV states that “each personality state may be experienced as if it has a

distinct personal history, self-image, and identity, including a separate name” (APA, 1994).

2.2.3.2. Somatoform dissociative symptoms

Dissociation also manifests in disturbances of sensations, movement and other bodily functions

(Nijenhuis et al., 1999). Nijenhuis and coworkers have labelled these disruptions as ‘somatoform

dissociation’ (Nijenhuis et al., 1996). Somatoform dissociative symptoms include different kinds of

functional or perceptual losses (sensation, pain, motor action), and/or intrusion symptoms of bodily

sensations and movements (e.g. tics), and pseudoseizures (Nijenhuis et al., 1998a). In the

development of the Somatoform Dissociation Questionnaire (SDQ-20), 20 items were selected from

75 items that best reflected instances of somatoform dissociation (Nijenhuis et al., 1996). From

these 20 items, the five that could best characterize ‘hysteria’ according to Janet were further

selected to form a short screening instrument, the SDQ-5. These include insensitivity to pain

29

(analgesia), the sensation of disappearance of the body or parts of it (kinaesthetic anaesthesia),

retraction of the visual field (visual anaesthesia), and difficulty in speaking or the inability to speak

(motor disturbance), as well as a specific symptom, i.e. pain while urinating (Nijenhuis et al., 1997).

In a Finnish non-clinical sample a clear link was found between visual distorsions (micropsia,

macropsia, metamorphopsia and teleopsia) and dissociation (Lipsanen et al., 1999).

2.2.3.3. Dissociative symptoms according to the Structural Dissociation Theory

In their book “The Haunted Self” (Van der Hart et. al, 2006), three leading researchers on

dissociation, Onno Van der Hart, Ellert Nijenhuis and Kathy Steel, have proposed their new theory

of structural dissociation of the personality in combination with a Janetian psychology of action.

According to the theory of structural dissociation, the key concept of understanding traumatization

is dissociation. Based on this theory they have also developed a model of phase-oriented treatment

that focuses on the identification and treatment of structural dissociation and related maladaptive

mental and behavioural actions.

Janet’s clinical observations suggested that hysteria involves psychological and somatoform

functions and reactions. In his view, mind and body were inseparable; thus, his classification of

dissociative symptoms does not follow a body-mind distinction. He divided dissociative symptoms

into permanent symptoms, “mental stigmata”, which mark all cases of hysteria, and “mental

accidents”, which are incidental and depend on each case. “Mental stigmata” include functional

losses such as the partial or complete loss of knowledge (amnesia), loss of sensations including

tactile sensations, kinaesthesia, smell, taste, hearing, vision and pain sensitivity (analgesia), and loss

of motor control (inability to move or speak). In the recent literature they have been referred to as

negative dissociative symptoms. “Mental accidents” represent positive symptoms because they

involve additions, i.e. mental phenomena, that should have been integrated in the personality, but

because of integrative failure become dissociated material that intrudes into the consciousness at

times. Examples include re-experiencing more or less complete traumatic memories and

manifestations of dissociative personality states (Nijenhuis, 2000). The phenomenological

categorization of dissociative symptoms according to the Structural Dissociation Theory is

presented in Table 1.

Based on the work of Charles Myers with (“shell-shocked”) World War I combat soldiers (Van

der Hart et al., 2000), the authors describe the division of the personality in terms of dissociative

parts of the personality. This choice of term emphasizes the fact that dissociative parts of the

personality together constitute one whole, yet are self-conscious, have at least a rudimentary sense

30

of self, and are generally more complex than a single psychobiological state (Van der Hart et al.,

2006).

In traumatized individuals the simplest dissociative division of the personality is primary

structural dissociation. It consists of a single apparently normal part of the personality (ANP) and a

single emotional part of the personality (EP). This division of the personality seems to evolve most

often in relation to a single traumatizing event, and the primary structural dissociation characterizes

simple trauma-related disorders, such as simple forms of post-traumatic stress disorders (PTSD) or

conversion disorders. However, the dissociative organization of the personality can be much more

complex, particularly in those who have experienced chronic childhood abuse and neglect (Van der

Hart et al., 2006). In general, more severe forms of traumatization involve greater levels of

dissociative symptoms (Chu et al., 1999; Draijer and Langeland, 1999; Teicher et al., 2006).

Adults may develop forms of complex trauma-related structural dissociation when their

traumatization is prolonged and repeated. Such adult trauma includes war, torture and internment in

concentration camps. However, it may be that most adults who develop secondary structural

dissociation do so because they have already been traumatized in childhood (Donovan et al., 1996).

In secondary structural dissociation of the personality, chronically traumatized individuals may

experience further division of their personality, resulting in a single ANP and more than one EP.

These EPs may be more elaborated than those in primary structural dissociation, and take not only

physical defensive characteristics, but also contain rigid and maladaptive mental defensive action

tendencies (Van der Hart et al., 2006).

Tertiary structural dissociation involves not only more than one EP, but also more than one ANP.

It is the most complex form of structural dissociation and is typical of many cases of dissociative

identity disorder (DID). In such cases, the action systems of daily life, such as exploration,

attachment and care-taking, which are found in a single ANP in primary and secondary structural

dissociation, are now divided among several ANPs. DID patients may continue to develop

additional ANPs because daily life may be overwhelming due to a difficult environment, internal

chaos from conflicts among dissociative parts of the personality, and chronic reactivation of

traumatic memories. The more complex the structural dissociation is, the more likely one or several

parts of the personality are to emancipate and act autonomously (Van der Hart et al., 2006).

31

Table 1. The phenomenological categorization of dissociative symptoms (Van der Hart et al.,

2006).

Psychoform dissociative symptoms Somatoform dissociative symptoms

Negative dissociative Loss of memory: dissociative amnesia Loss of sensations: anaesthesia

symptoms Depersonalization involving a division (all sensory modalities)

between experiencing and observing Loss of pain sensitivity: analgesia

part of the personality Loss of motor actions, i.e. loss of the

Loss of affect: emotional anaesthesia ability to move (e.g. catalepsy), speak,

Loss of character traits swallow, etc.

Positive dissociative Psychoform intrusion symptoms Somatoform intrusion symptoms,

symptoms (Schneiderian symptoms), e.g. e.g. “made” sensations and body

hearing voices, “made” emotions, movements (e.g. tics)

thoughts, and ideas Pseudoseizures

Psychoform aspects of re-experiencing Somatoform aspects of

traumatizing events, e.g., particular re-experiencing traumatizing events,

visual and auditory perceptions, affects, e.g., particular trauma-related

and ideas sensations and body movements

Psychoform aspects of alterations between Somatoform aspects of alterations

dissociative parts of the personality between dissociative parts of the

personality

Psychoform aspects of dissociative psychosis, Somatoform aspects of dissociative

i.e., a disorder involving a relatively psychosis

long-term activation of a psychotic

dissociative part

2.2.4. Dimensional or categorical construct?

The dimensional model of dissociation proposes that dissociation represents a continuous

construct, and it is experienced to a lesser or greater degree by all people. The hypothesis that

dissociation is a normal process that is initially used defensively by an individual to handle

traumatic experiences and evolves over time into a maladaptive or pathological process has been

expressed in a variety of forms over the years, for example by Morton Prince at the beginning in the

32

20th century (Putnam 1989). Ernest Hilgard (1974, 1984), with his neodissociative theory of the

mind, was one of the most instrumental modern figures advocating the concept of a continuum of

dissociation from the normal to the pathological (Putnam, 1989). Hilgard (1984) characterized

hypnosis as a state which produces a certain readiness for dissociative experiences. Thus, evidence

to support the idea of a dissociative continuum comes from research on the distribution of hypnotic

susceptibility in either normal or patient populations. Patients with dissociation and post-traumatic

disorders have most frequently been found to be highly hypnotizable, whereas those with affective

or anxiety disorders, or schizophrenia were relatively less hypnotizable (Carlson and Putnam, 1989;

Spiegel et al., 1988).

The development of the Dissociative Experiences Scale (DES) (Bernstein and Putnam, 1986)

was consistent with the dimensional model of dissociation. The DES assesses a person’s standing

on one or more dissociative dimensions. Most studies using the DES have relied on statistical

procedures for dimensional reduction (Akûyz et al., 1999; Frischholz et al., 1992; Ross et al., 1990).

The DES was explicitly constructed to be a stable trait measure of dissociative experiences (Carlson

and Putnam, 1993).

Later, it was observed that dissociative symptoms are dichotomously distributed, and the

frequency and type of dissociative experiences reported by members of certain diagnostic groups

have suggested “the existence of two or more dissociation types” (Putnam et al., 1996). This finding

was investigated and confirmed by Waller and coworkers (Waller at al., 1996; Waller and Ross,

1997), who made the crucial distinction between items that are pathognomonic of dissociative

disorders and unlikely to be widely endorsed (e.g. “Some people sometimes have the experience of

feeling that other people, objects, and the world around them are not real”) and those that are not

inherently pathological and likely to be widely endorsed by persons in normal as well as clinical

samples (e.g. “Some people find that when they are watching television or a movie they become so

absorbed in the story that they are unaware of other events happening around them”). Waller and

coworkers (1996) suggested that these non-pathological phenomena were manifestations of a

dissociative trait, qualitatively different from the pathological type of dissociation. The 8-item

subscale (DES-T) of pathognomonic items from the DES was developed to identify individuals who

experience pathological dissociation (Waller at al., 1996; Waller and Ross, 1997). Taxometric

methodology and analyses were undertaken with the DES and yielded two distinct classes or

groups; one group comprised members of a taxon who demonstrated pathological dissociation

while the remainders were non-taxon members (Waller et al., 1996). The identification of the

dissociative taxon marks a return to Janet’s original conceptualisation of dissociation as a

33

discontinuity of awareness experienced only by the mentally unwell (Putnam et al., 1996; Waller et

al., 1996).

According to this categorical conceptualization of dissociative phenomena, the distinction

between normal and pathological dissociation represents not only a difference in degree but also a

difference of type (Waller et al., 1996). This conceptualisation explicitly moves the concept of

pathological dissociation away from a dimension or trait model to a discrete or typological

construct and distinguishes pathological forms of dissociation from more “normal” dissociative

states such as day-dreaming. However, there is still controversy over whether dissociation is a

dimensional or categorical construct. Some studies have found support for the taxonic model of

dissociation (Allen et al., 2002; Irwin, 1999), but contradictory results have also been obtained

(Simeon et al., 2003; Watson, 2003).

2.2.5. Dissociation as a disorder and the classification of dissociative disorders

According to the Diagnostic Manual for Mental Disorders, Fourth edition (DSM-IV, American

Psychiatric Association, 1994), the essential feature of dissociation is “a disruption of the normal

integrative functions of consciousness, memory, identity, and perception of the environment”. The

classification of somatoform disorders and the former “construct with a hysterical root” remains an

area of division between the DSM-IV and the International Statistical Classification of Diseases and

Related Health Problems (ICD-10, WHO, 1992). The main difference is that what was originally

considered as hysteria has been divided into several independent categories in the current DSM

classification, but in the ICD-10, Conversion and Dissociation categories are inseparable. In the

DSM-IV, the Conversion disorders are within the broader Somatoform disorders category. This

separation in the DSM-IV emphasizes the importance of excluding organic illness (such as

neurological illnesses) when diagnosing these conditions (APA, 1994). The ICD-10 excludes the

depersonalization-derealization disorder from the Dissociative (conversion) disorders on the

grounds that it does not involve a major loss of control over sensation, memory or movement, and is

associated with only minor changes in personal identity (WHO, 1992). The DSM-IV includes a

distinct category for dissociative identity disorder (DID), which is placed (using its former name in

the DSM of multiple personality disorder) in the Other dissociative (conversion) disorders category

in the ICD-10, reflecting controversy over this condition. DSM-IV also requires the presence of at

least three dissociative symptoms for acute stress disorder (ASD), whereas dissociative symptoms

are not a requirement for ASD in the ICD-10. Post-traumatic stress disorder (PTSD) is not

categorized as a dissociative disorder in either the ICD-10 or DSM-IV. These inconsistencies

34

between the DSM-IV and the ICD-10 illustrate the confusion that surrounds the dissociation

concept. A synopsis of the classification of dissociative disorders with comparisons between the

ICD-10 and the DSM-IV-TR (APA, 2000) is presented in Table 2.

There are also differences in the general criteria: the ICD-10 requires convincing associations in

time between the onset of symptoms of dissociative disorders and stressful events, problems, or

needs, but this is not mentioned in the DSM classification. The DSM-IV states that dissociative

symptoms must cause clinically significant distress or impairment in social, occupational or other

important areas of functioning, but the above rule is not included in the ICD-10. With the

development and new formulations of the DSM classification, the dissociative disorders have been

described and categorized differently.

35

Table 2. A synopsis of the classification of dissociative disorders with comparisons between

the ICD-10 and DSM-IV-TR (Lipsanen, 2004).

Code ICD-10 Code DSM-IV-TR

F44.0 Dissociative amnesia 300.12 Dissociative amnesia

F44.1 Dissociative fugue 300.13 Dissociative fugue

F44.2 Dissociative stupor No corresponding category, code as 300.15

Dissociative disorder NOS

F44.3 Trance and possession No corresponding category, code as 300.15

disorders Dissociative disorder NOS

F44.4 Dissociative motor 300.11 Conversion disorder with motor symptom

disorder or deficit

F44.5 Dissociative convulsions 300.11 Conversion disorder with seizures

or convulsions

F44.6 Dissociative anaesthesia 300.11 Conversion disorder with seizures

and sensory loss or convulsions

F44.7 Mixed dissociative 300.11 Conversion disorder with sensory symptom

(conversion) disorders or deficit

F44.8 Other dissociative No corresponding category, code as 300.15

(conversion) disorders Dissociative disorder NOS

F44.80 Ganser’s syndrome No corresponding category, code as 300.15

Dissociative disorder NOS

F44.81 Multiple personality 300.14 Dissociative identity disorder

disorder

F44.82 Transient dissociative No corresponding category, code as 300.15

(conversion) disorders Dissociative disorder NOS

occurring in childhood

and adolescence

F44.88 Other specified No corresponding category, code as 300.15

dissociative (conversion) Dissociative disorder NOS

disorders

F44.9 Dissociative (conversion) 300.15 Dissociative disorder NOS

disorders, unspecified

F48.1 Depersonalization-derealization 300.6 Depersonalization disorder

disorder

F06.5 Organic dissociative disorder No corresponding category, code as 294.9

Cognitive disorder NOS

36

2.3. Biological factors in dissociative pathology

Smaller hippocampal volumes have been reported in several stress-related psychiatric disorders,

including post-traumatic stress disorder (PTSD) (Bremner et al., 1997, 2003), borderline personality

with early abuse (Driessen et al., 2000), and depression with early abuse (Vythilingham et al.,

2002). Excessive amygdaloid activation has been proposed to play a crucial role in the development

of PTSD (Rauch et al., 1996), and in triggering fight-or-flight responses (Lee et al., 1998).

Although dissociative disorders and especially dissociative identity disorder have been associated

with usually multiple, sustained forms of childhood maltreatment (Anderson et al., 1993; Boon and

Draijer, 1993; Tutkun et al., 1998), there is relatively little knowledge of the biological basis of

dissociative disorders.

Vermetten and coworkers (2006) found that the hippocampal and amygdalar volumes were

smaller in patients with dissociative identity disorder (DID) with comorbid PTSD compared with

healthy controls. The volume reductions were larger in the amygdala than in the hippocampus. It

was suggested that DID would be associated with relatively greater volume reductions in the

amygdala than in the hippocampus.

Apart from single case reports (Mathew et al., 1985, Saxe et al., 1992; Tiihonen et al., 1995),

regional cerebral blood flow (SPECT) has been studied in a sample of 15 patients with dissociative

identity disorder and eight healthy control subjects ( ar et al., 2001). Perfusion differences were

found in orbitofrontal regions bilaterally and the left lateral temporal region among patients with

DID compared with control subjects. Among patients with DID, different cognitive and emotional

characteristics of alter personality states were also observed in order to screen state-dependent

perfusion changes, but no such evidence was found. It was suggested that the observed perfusion

pattern in the DID patients was a trait characteristic rather than a state dependent one ( ar et al.,

2001).

Flor-Henry and coworkers (1990) documented two cases of multiple personality disorder with

left hemisphere activation in EEG analysis and bilateral frontal and left temporal dysfunction in

neurophysiological test batteries. These results were interpreted as resulting from the disruption of

intrahemispheric inhibition (Flor-Henry et al., 1990). It has also been suggested that some

personality shifts may be associated with activation and transition to the right hemisphere dominant

mode (Teicher et al., 2002). In a Finnish non-clinical sample of 297 adults, in addition to female sex

and younger age, non-right handedness accounted for 24% of the total variance of the DES. It was

hypothesized that non-right handedness was a predisposing factor for dissociative episodes,

especially in female subjects (Lipsanen et al., 2000).

37

2.4. Assessment of dissociative symptoms with questionnaires

There are several psychometric measures to quantify dissociative symptoms among individuals.

The purpose of the development of these measures has been to help identify patients with

dissociative psychopathology by screening with self-report questionnaires, and as a research tool to

provide a means to quantify dissociative experiences and symptoms.

2.4.1. The Dissociative Experiences Scale (DES)

The most commonly used instrument to assess dissociation is the Dissociative Experiences Scale

(DES) (Bernstein and Putnam, 1986). It is a 28-item self-report questionnaire to measure

psychological aspects of dissociation. The DES is based on the concept of dissociation as a

continuum from minor dissociations of everyday life to major forms psychopathology (Bernstein

and Putnam, 1986). The DES was developed to be a trait measure of dissociation and it inquires

about the frequency of dissociative experiences in daily life. It has been shown to have good

internal reliability, strong convergent validity with other measures of dissociation across 26 studies,

and discriminant validity in distinguishing dissociative disorders from other diagnostic groups (Van

Ijzendoorn and Schuengel, 1996). The DES has a four-week test-retest stability of 0.93 (Frischholz

et al., 1990).

The first version of the DES utilized a visual analogy scale consisting of a 100-mm line

numerically anchored at endpoints but with no divisions. The subject was instructed to indicate his

or her response to each question by making a slash across the 100-mm line at the appropriate place.

The response was scored by using a ruler to measure the distance in millimetres from the zero point

to the slash mark (Bernstein and Putnam, 1986). In the second version (DES II), subjects were

asked to indicate with a circle on a visual analogy scale what percentage (0%-100%) of the time

within ten percentage points they experienced dissociative symptoms. The individual’s total score

was the mean of the 28 items, and higher scores indicated greater levels of dissociation. The DES II

has some advantages compared with the DES I, as it is easier to score and response choices are

clearer (Ellason et al., 1991). The second version has almost entirely replaced the first version in

research and clinical settings, and was used in this study.

The DES has been divided in three factors or subscales (Carlson and Putnam, 1993) that each

measure different aspects of dissociative experiences. The absorption and imaginative involvement

factor (DES-ABS) has mostly been considered to reflect the nonpathological aspects of

38

dissociation. The amnestic (DES-AMN) and depersonalization-derealization (DES-DD) factors

have consisted more of questions measuring pathological dissociation.

A Dissociative Experiences Scale Taxon (DES-T) with eight items (numbers 3, 5, 7, 8, 12, 13,

22, and 27) from the DES has been developed to more clearly distinguish the pathological

component of dissociation (Waller et al., 1996; Waller and Ross, 1997). This scale measures

identity alteration, depersonalization, derealization, discontinuation of awareness, dissociative

amnesia, and auditory hallucinations. The typological model suggests that an individual either

belongs to a pathological dissociative taxon or not, and that nonpathological dissociation is a

dimensional phenomenon. The taxon membership probabilities can be calculated with a statistical

program on the basis of the weights for each DES-T item score (Waller and Ross, 1997 p. 510). It is

also possible to calculate the unweighted mean of the DES-T items, and choose different cut-off

scores to measure significant levels of pathological dissociation (Ross et al., 2002; Waller and Ross,

1997).

Various cut-off scores of the DES have been used to identify those who might have a

dissociative disorder or a disorder with a considerable dissociative component. Cut-off scores of 15-

30 have been suggested to distinguish subjects with significant dissociative symptomatology

(Draijer and Boon, 1993; Ross et al., 2002; Steinberg et al., 1991; Waller at al., 2001; Waller and

Ross, 1997). The DES is not, however, a diagnostic tool. To obtain a reliable diagnosis, subjects

with high DES scores should be interviewed either using the complete DES questionnaire or

structured clinical interviews for dissociative disorders such as for example the Structured Clinical

Interview for DSM-III-R Dissociative Disorders (SCID-D) (Steinberg et al., 1991, 1993) or the

Dissociative Disorders Interview Schedule (DDIS) (Ross et al., 1989; Ross and Ellason 2005).

2.4.2. The Somatoform Dissociation Questionnaire (SDQ-20)

The Somatoform Dissociation Questionnaire (SDQ-20) was developed in 1996 by Ellert

Nijenhuis and his coworkers to assess the somatoform components of dissociation (Nijenhuis et al.,

1996). The SDQ-20 is a self-report questionnaire of 20 items. An individual is asked to identify to

what extent each statement is applicable to him or her. Items include such statements as “My body,

or part of it, feels numb”, “I can’t swallow, or only with great effort”, and “My body, or part of it, is

insensitive to pain”. The score corresponding to the response to each statement ranges from 1 to 5,

and the total score from 20 to 100. The SDQ-20 has excellent internal consistency, strong

convergent validity with the DIS-Q and the DES (Nijenhuis et al., 1996, 1999) and construct

validity as measured by its correlation with reported trauma (Nijenhuis et al., 1998c).

39

The SDQ-20 has not previously been used in general population samples, but it has been used

with dissociative disorder patients, patients from other different diagnostic categories and non-

clinical participants (El-Hage et al., 2002; Espirito Santo and Pio-Abreu, 2007; Nijenhuis, 2000; ar

et al., 2000). With a cut-off score of 30, patients with DSM-IV dissociative disorders were

discriminated from psychiatric patients with other disorders with a sensitivity of 0.90 and a

specificity of 0.75 ( ar et al., 2000). A recent study compared dissociative disorder patients with

patients from other diagnosis groups, where a cut-off score of 35 was found optimal for differential

diagnosis in a clinical sample (Espirito Santo and Pio-Abreu, 2007).

A brief five-item screening version of the SDQ-20 has been developed by the same authors, the

SDQ-5 (Nijenhuis et al., 1997). The five items include insensitivity to pain (analgesia), the

sensation of disappearance of the body or parts of it (kinesthetic anaesthesia), retraction of the

visual field (visual anaesthesia), difficulty in speaking or the inability to speak (motor disturbance),

and pain while urinating. However, the SDQ-5 has been shown to be more vulnerable to cultural

differences than the original SDQ-20 ( ar et al., 2000).

2.4.3. Other measures

Other self-administrated scales to measure dissociative experiences have been developed, but

their use in clinical or non-clinical samples has been more infrequent than the use of the DES or the

SDQ-20. Both the Multidimensional Inventory of dissociation (MID) and the Dissociation

Questionnaire (DIS-Q) include considerably more items compared with the DES or the SDQ-20,

and are thus not as suitable for large epidemiological surveys.

2.4.3.1. The Dissociation Questionnaire (DIS-Q)

The Dissociation Questionnaire (DIS-Q) was the first European clinical scale to assess

dissociation (Vanderlinden et al., 1991). It is a 63-item, self-report instrument with a five-point

Likert format. Its four scales (i.e. identity confusion and fragmentation, loss of control, amnesia,

absorption) have good internal consistency and a three-to-four-week test-retest stability. The DIS-Q

has discriminated dissociative disorder patients from normal adults and other psychiatric patients

(Vanderlinden et al., 1993).

40

2.4.3.2. The Adolescent Dissociative Experiences Scale (A-DES)

The Adolescent Dissociative Experiences Scale (A-DES) is a questionnaire for screening

dissociation during adolescence. It is a 30-item self-report questionnaire with an 11-point scale

ranging from “never” to “always” (Armstrong et al., 1997). It was used in a Finnish sample of 4019

adolescents, where a high level of dissociation was associated with an age of 15 or less, daily

smoking, frequent use of alcohol, abuse of legal drugs, cannabis use, social isolation and poor

performance in mathematics (Tolmunen et al., 2007).

2.4.3.3. The Multidimensional Inventory of dissociation (MID)

The MID is a 218-item, self-administrated multiscale instrument that comprehensively assesses

the phenomenological domain of pathological dissociation and diagnoses dissociative disorders. It

was designed for clinical research and for diagnostic assessment of patients who present with a

mixture of dissociative, post-traumatic and borderline symptoms. The MID has demonstrated

internal reliability, temporal stability, convergent validity, discriminant validity and construct

validity (Dell, 2006a). The MID has been used in a study with dissociative identity disorder patients

to comprehensively evaluate all dissociative symptom modalities (Dell, 2006b).

2.5. Dissociation in the general and non-clinical population

2.5.1. Prevalence of dissociative symptoms in general and non-clinical populations

2.5.1.1. Prevalence of psychological dissociation

The majority of non-clinical or general population studies have used the DES as a measurement

scale for dissociation (Akyüz et al., 1999, 2005; Lipsanen et al., 2003; Putnam et al., 1996; Ross et

al., 1990; Xiao et al., 2006a), or a modified version of the DES (Mulder et al., 1998). In two studies,

pathological dissociation was measured with the eight-item DES-Taxon (Seedat et al., 2003; Spitzer

et al., 2006). The DIS-Q has been used in one general population study (Vanderlinden et al., 1991).

A summary of these previous studies is presented in Table 3.

41

Studies on general populations have demonstrated that dissociative experiences are quite

common, and their prevalence has ranged from 1.0% to 12.8% (Akyüz et al., 1999, Ross et al.,

1990), depending on the scale used or on the cut-off point selected to indicate a high level of

dissociation. Among a general population sample of Turkish females, 15.9% of the participants

scored over 20 in the DES (Akyüz et al., 2005). Other studies (Putnam et al., 1996; Waller and

Ross, 1997) have questioned the highest estimates of the prevalence of dissociative disorders in the

general population. Instead of considering dissociation as a continuum from normal to pathological,

a typological model has been developed (Waller and Ross, 1997). The prevalence of pathological

dissociation (DES-T 20) has been found to be 4.4% in the North American general population

(Seedat et al., 2003). The prevalence of DES-taxon membership was reported as 3.3% in the

Canadian general population (Waller and Ross, 1997), but it was much lower in German (0.3%;

Spitzer et al., 2006) and Chinese (0.5%; Xiao et al., 2006a) non-clinical population samples.

The lowest mean DES score of 2.6 (SD 4.3) has been detected among a Chinese non-clinical

population sample of factory workers (Xiao et al., 2006a). In other studies the mean DES score has

ranged from 6.7 (SD 6.1) in a Turkish general population (Akyüz et al., 1999) to 10.8 (SD 10.2) in a

Canadian general population sample (Ross et al., 1990). Among the Turkish female general

population the mean DES score was 11.8 (SD 10.2) (Akyüz et al., 2005).

2.5.1.2 Prevalence of somatoform dissociation

Until now, no studies on the prevalence of somatoform dissociation in the general population have

been published. There have been only two studies on non-clinical samples in which the mean SDQ-

20 score has been reported. One of these was carried out on a Turkish non-clinical population ( ar

et al., 2000), including 175 participants aged 18-64 years (mean age 30.3 years [SD 9.4]). The mean

SDQ-20 score of this sample was 27.4 (SD 8.2). The other study included a random Dutch sample

of 147 subjects with an age range of 19-77 years, and also a student sample of 73 participants aged

17 to 29 years (mean age 21.8 years [SD 2.3]). The mean SDQ-20 score in these groups was 23.2

(SD 5.0) and 24.4 (SD 4.4), respectively (Näring and Nijenhuis, 2005).

.

42

Table 3. Prevalence of high dissociation and mean scores from questionnaires on dissociation

in non-clinical population samples.

Author(s) Sample Female% Questionnaire Prevalence of high Mean score

year, country (Age/mean age ± SD) for measuring dissociation (± SD)

dissociation

Akyüz et al. 994 (18-65/34.7 ± 12.9) 47.2 DES DES 20 in 3.8% 6.7 (± 6.1)

1999, Turkey general population DES 30 in 1%

Lipsanen et al. 924 (18-64/40.1 ± 12.6) 60.0 DES 8.4 (± 7.9)

2003, Finland non-clinical population

Mulder et al. 1028 (18 yrs or more) DES 15 items of the DES

1998, New Zealand general population occurring often to

always in 6.3%

Putnam et al. 415 (22 yrs or more/40.5) DES DES 30 in 4.4% 8.3 (± 9.3)

1996, United States non-clinical population

and Canada

Ross et al. 1055 (20 yrs or more/ 58.3 DES DES 20 in 12.8% 10.8 (± 10.2)

1990, Canada 43.2 ± 16.7) DES 30 in 5%

general population

Seedat et al. 1007 (18-65/39.6 ± 13.0) 63.3 DES-T DES-T 20 in 4.4% 3.5 (± 8.6)

2003, United States general population DES-T 30 in 2%

Spitzer et al. 297 (18-77/39.0 ± 13.2) 58.2 DES-T DES-taxon 0.3% 2.3 (± 4.2)

2006, Germany non-clinical population DES-taxon

Vanderlinden et al. 374 (10 yrs or more) 49.4 DIS-Q DIS-Q 2.5 in 3% 1.7 (± 0.45)

1991, Belgium and general population in men

Netherlands DIS-Q 3.5 in 1% 1.6 (± 0.37)

in women

Waller and Ross, 1055 (20 yrs or more/ 58.3 DES-taxon DES-taxon 3.3%

1997, Canada 43.2 ± 16.7)

general population

Xiao et al. 618 (41.7 ± 5.9) 52.0 DES DES-taxon 0.5% 2.6 (± 4.3)

2006, China non-clinical population DES-taxon

43

2.5.2. Factors associated with dissociation

2.5.2.1. Sociodemographic factors

2.5.2.1.1. Age

A negative association between age and dissociation scores measured with the DES (Akyüz et

al., 1999; Lipsanen et al., 2000; Ross et al., 1990) or DIS-Q (Vanderlinden et al., 1991) has been

observed in general population samples. Pathological dissociation (DES-T) was also found to be

associated with a younger age (Seedat et al., 2003).

In most studies, age has not influenced the SDQ-20 scores (El-Hage et al., 2002; Nijenhuis,

2000), but in a Turkish mixed sample with clinical and non-clinical participants a weak but

statistically significant correlation was found between the SDQ-20 scores and age ( ar et al., 2000).

2.5.2.1.2. Sex

A meta-analytic study summarizing 19 clinical and non-clinical studies reporting scores for both

men and women concluded that there was no gender difference in dissociative pathology (Van

Ijzendoorn and Schuengel, 1996). In a large German sample of nonclinical and clinical subjects no

gender difference was found in the total DES scores, absorption or pathological dissociation scores.

The only significant difference was in the amnesia subscale of the DES: men scored higher

compared with women (Spitzer et al., 2003). Female subjects scored higher in the DES in a non-

clinical Finnish sample (Lipsanen et al., 2000). In one general population study, pathological

dissociation (DES-T) was associated with male gender (Seedat et al., 2003).

No difference has been observed between the Somatoform Dissociation Questionnaire (SDQ-20)

scores of male and female subjects in the majority of clinical and non-clinical samples (Nijenhuis et

al., 1996, 1998a; ar et al., 2000), but in a French outpatient sample women had higher scores than

men (El-Hage et al., 2002).

2.5.2.1.3. Sosioeconomic and marital status

In the Turkish general population, married subjects had lower DES scores compared with single

subjects (Akyüz et al., 1999), but high dissociation scores have not otherwise generally been

44

associated with marital status or with educational or economic level (Ross et al., 1990).

Pathological dissociation was associated with African-American ethnicity (Seedat et al., 2003).

A negative correlation between high somatoform dissociation, educational level and socio-

economic status was detected in a Turkish sample of clinical and non-clinical participants ( ar et

al., 2000).

2.5.2.2. Adverse Childhood Experiences

The hypothesis that dissociation occurs in response to trauma has a long tradition in psychiatry

from the beginning of the modern research on hysteria and dissociation in the 19th and 20th century

(Van der Hart and Horst, 1989). Dissociation was believed to be used as a means of a defence or an

attempt to adapt to the traumatic experiences; if the extent of the abuse is sufficient, then the

dissociative response regularly becomes relied upon as a defence mechanism and the individual’s

mental processes become intermittently fragmented (Irwin, 1994). The consequences of childhood

sexual and physical abuse and their impact on dissociative symptom formation has been the focus

of dissociation research (Chu and Dill, 1990; Mulder et al., 1998; Van der Kolk et al., 1996), but in

recent years various and multiple forms of childhood maltreatment or adverse childhood

experiences have been studied.

In a large ACE study (Felitti et al., 1998), the categories of adverse childhood experiences were

strongly interrelated and persons with multiple categories of childhood exposure were likely to have

multiple health risk factors in later life. A positive, graded relationship between ACEs and

attempted suicide (Dube et al., 2001), as well as hopelessness (Haatainen et al., 2003), has been

found at the population level. When the association between multiple types of childhood

maltreatment and several outcome measures (including dissociation, depression and anxiety) was

investigated in a non-clinical population of 554 subjects, exposure to multiple forms of

maltreatment was observed to have an effect size that was often greater than the component sum

(Teicher et al., 2006).

In the general population, traumatic experiences have been associated with psychological

dissociation. However, the existence of a direct causal relationship between childhood sexual abuse

and dissociation has been questioned, because of the indirect association with high dissociation: it

was related to both physical abuse and the current mental state (Mulder et al., 1998). Among the

Dutch general population, those subjects with a trauma history had higher scores in the Dissociation

Questionnaire (DIS-Q) compared to subjects with no trauma (Vanderlinden et al., 1993). A recent

study on a non-clinical sample of young adults also showed that combined exposure to parental

45

verbal aggression and witnessing domestic violence was associated with an extraordinarily large

effects size on dissociation, and the association was even stronger than with familiar sexual abuse

(Teicher et al., 2006). Sexual abuse, physical neglect and emotional abuse were associated with a

diagnosis of a dissociative disorder among women in the general population ( ar et al., 2007),

although an earlier study in the same district found no significant associations between high

dissociation and traumatic experiences (Akyüz et al., 1999).

Somatoform dissociation has been shown to be associated with childhood abuse in clinical

samples (Nijenhuis et al., 1998c; Roelofs et al., 2002; Waller et al., 2000). Among various types of

trauma, physical abuse, with an independent contribution of sexual trauma, best predicted

somatoform dissociation. Both psychological and somatoform dissociation were best predicted by

an early onset of reported intense, chronic and multiple traumatization (Nijenhuis et al., 1998c).

Waller and coworkers found that somatoform dissociation was especially associated with physical

abuse and a threat to life from another person (Waller et al., 2000). The relationship between

childhood traumatic experiences and somatoform dissociation has also been examined in two non-

clinical samples (Näring and Nijenhuis, 2005).

2.5.2.3. Other psychiatric conditions

2.5.2.3.1. Depression and suicidality

In clinical samples, dissociative disorder patients frequently have comorbid current depression or

a history of major depression (Ellason et al., 1996; Lipsanen et al., 2004a; ar et al., 2004; Yargic et

al., 1998). A study with depersonalization disorder patients found considerable comorbidity

between depersonalization disorder and depression (Baker et al., 2003). Furthermore, in a study on

chronic pelvic pain patients, dissociative disorders were closely associated with self-reported

anxiety and depression, and with DES scores (Nijenhuis et al., 2003).

At the population level, three studies have examined the association between high dissociation

and comorbid mood disorders/major depression. No statistically significant association was found

between high dissociation (DES>17) and a diagnosis of major depression among the Turkish

general population (Akyüz et al., 1999), but among the general population in New Zealand an

association between dissociative symptoms and mood disorders was detected (Mulder et al., 1998).

In a recent study on a sample of the female Turkish general population, participants with a

dissociative disorder had major depression more frequently than those without a dissociative

disorder ( ar et al., 2007).

46

Patients with dissociative disorders frequently engage in self-destructive behaviour (Low et al.,

2000; Saxe et al., 2002). Many patients who have self-mutilative behaviours report feeling numb

and dead prior to harming themselves. Although self-mutilation is different from actual suicidality

(Pattison and Kahan, 1983), a strong relationship between dissociation, suicide attempts and self-

mutilation has been found in a large non-clinical sample (Zoroglu et al., 2003). Among the general

population of female subjects in Turkey, participants with a dissociative disorder more often had a

history of suicide attempts than those without a dissociative disorder ( ar et al., 2007).

In Dutch samples, the SDQ-20 scores were low among patients with mood disorders, especially

among patients with bipolar mood disorder (Nijenhuis, 2000). To my best knowledge, no studies

have yet examined the possible association between high somatoform dissociation and suicidal

ideation.

2.5.2.3.2. Other psychiatric disorders

Dissociative symtoms have been highly correlated with psychopathology (Putnam et al., 1996;

Saxe et al., 1993). The comorbidity of high dissociation, dissociative disorders and other psychiatric

disorders has been examined in three general population studies (Akyüz et al., 1999; Mulder et al.,

1998; ar et al., 2007) with structured clinical interviewing methods. Akyüz and coworkers found

no association between high dissociation and other diagnostic categories. Post-traumatic stress

disorder (PTSD) and anxiety disorders were associated with high dissociation in New Zealand

(Mulder et al., 1998). Turkish female participants with dissociative disorders had borderline

personality disorder, somatisation disorder, and PTSD more frequently than did participants with a

dissociative disorder ( ar et al., 2007). Only recently, associations between dissociation and

childhood attention-deficit-hyperactivity-disorder (ADHD) have been proposed (Endo et al., 2006;

Matsumoto and Imamura, 2007).

In clinical samples, high somatoform dissociation has been associated with somatoform

disorders (somatisation and conversion disorders) (Espirito Santo and Pio-Abreu, 2007; Nijenhuis,

2000), eating disorders (Nijenhuis, 2000; Waller et al., 2003) and PTSD (Espirito Santo and Pio-

Abreu, 2007). Somatoform dissociation showed particularly strong links with the presence of

bulimic behavioural features and bulimic attitudes (Waller et al., 2003).

47

2.5.2.4. Alexithymia

The association between alexithymia and dissociation has been examined in clinical and non-

clinical samples, but no studies have been published on the general population. Previous research

on the relationship between dissociation and alexithymia is summarised in Table 4. This

relationship has been discussed in the theory of psychodynamic medicine (Nemiah 1977, 1991,

2000). The construct of alexithymia was introduced by Sifneos (1973). Alexithymia, meaning ‘lack

of word, mood or emotion’, involves “reductions or incapacities to fantasize, experiences, and

verbalize emotions, and an absence of tendencies to think about one’s emotions” (Sifneos, 1973).

Alexithymia has been characterized by deficits in emotional communication, cognitive

processing and the regulation of emotions (Taylor, 2000). Both dissociation and alexithymia

represent symptoms of somatization (Nemiah, 1991), difficulties with affect regulation (Van der

Kolk et al., 1996) and possible associations with traumatic experiences (Chu and Dill, 1990; Cloitre

et al., 1997; Berenbaum, 1996). Long-lasting alexithymic features have been associated with harsh

discipline and unhappiness of the childhood home, depression at 12 months and major depressive

disorder at 24 months in a two-year follow-up study of patients with major depressive disorder

(Honkalampi et al., 2004).

Significant correlations between dissociation and alexithymia have been found, and the domain

“difficulty identifying feelings” of the TAS-20 has especially been associated with dissociative

symptomatology (Elzinga et al., 2002; Grabe et al., 2000; Irwin and Melvin-Helberg, 1997;

Modestin et al., 2002). However, it has been argued that a depressed mood accounts for the group

differences in scores between the Toronto Alexithymia Scale (TAS-20) and Dissociative

Experiences Scale (DES) (Wise et al., 2000). In two recent studies, despite their mutual

correlations, dissociation and alexithymia have been suggested to be different constructs (Lipsanen

et al., 2004b; Tutkun et al., 2004).

One study has examined the association between alexithymia and both psychoform and

somatoform dissociation (Clayton, 2004). In that study the Bermond Vorst Alexithymia

Questionnaire (BVAQ) was used to assess alexithymia and somatoform dissociation was the

strongest predictor of alexithymia. Somatoform dissociation was directly related to all facets of

alexithymia except for fantasizing.

48

Table 4. The relationship between dissociation and alexithymia in clinical and non-clinical

samples.

Author(s) Sample (Age/mean age ± SD) Assessment of dissociation Conclusion of the association

Year, Country and alexithymia

Clayton, 219 non-clinical participants DES, DES-T, Somatoform *No association between pathological

2004, Australia Dissociation Questionnaire (SDQ), dissociation and alexithymia

Bermont Vorst Alexithymia *Somatoform dissociation was strongly

Questionnaire (BVAQ) associated with alexithymia

Elzinga et al. 833 undergraduate students Dissociation Questionnaire DIS-Q, *Positive correlation between dissociation

2002, Netherlands 17-30 yrs/20.6 ± 2.8 Toronto Alexithymia Scale and ‘difficulty identifying feelings’

(TAS-20), BVAQ *Distinct constructs

Grabe et al. 173 patients and 38 German 44 item version *Significant correlations between dissociation

2000, Germany non-clinical participants, of the Dissociative Experiences and all dimensions of alexithymia

116 females (38.8 ± 13.2 yrs), Scale (FDS), TAS-20 *Alexithymic characteristics contribute to

95 males (40.2 ± 13.7 yrs the development of pathological dissociation

Irwin and Melbin- 100 undergraduate students Questionnaire of Experiences *‘Difficulty identifying feelings’ predicted

Helberg 18-52 yrs/21.9 yrs of Dissociation (GED), TAS-20 dissociative tendencies

1997, Australia *Verbal processing dissociated from

affective processes

Lipsanen et al. 924 non-clinical subjects DES, TAS-20 *Distinct constructs but correlate significantly

2004, Finland

Modestin et al., 276 medical students DES, TAS-20 *Alexithymic probands had high DES scores

2002, Switzerland 24.4 (SD 3.0) yrs *Positive correlation between dissociation and

‘difficulty identifying and describing feelings’

Tutkun et al., 154 outpatients DES, TAS-20 *Overall effect of dissociation was not significant

2004, Turkey TAS-20 61, 34.7 (SD 10.0) yrs on the TAS-20 total or subscale scores

TAS-20<60, 35.8 (SD 10.4) yrs *Dissociation is different from alexithymia

Wise et al. 116 outpatients DES, TAS-20 *Depressed mood accounted for the group

2000, USA DES<15, 42.6 (SD 13.4) yrs differences between the DES and TAS-20

DES 15, 39.7 (SD 12.6) yrs scores

*Dissociation differs from alexithymia

49

2.5.2.5. Substance use (alcohol and tobacco)

In the alcohol-dependant population, different results have been detected in relation to the level

of dissociative symptomatology (Schäfer et al., 2007). In the general population, associations were

found between substance use and high DES scores (Mulder et al., 1998), as well as harmful alcohol

use and DES-T scores (Seedat et al., 2003).

Exposure to traumatic events and PTSD have been associated with increased smoking (Feldner

et al., 2007; Van der Velden et al., 2007). In a sample of 4019 Finnish adolescents a high level of

2.5.2.6. Familiality

Contradictory results have been obtained in twin studies, where the relative influences of genetic

and environmental factors on dissociation have been estimated (Becker-Blease et al., 2004; Jang et

al., 1998; Waller and Ross, 1997). Waller and Ross (1997) found no genetic variance, and 45% of

the variance of the DES-T and taxon membership scores was attributable to the shared environment

(i.e. environmental influences that lead to sibling similarity in dissociation), while 55% was

attributable to the non-shared environment (i.e. environmental influences that lead to sibling

differentiation). In contrast to these findings, using taxon membership scores, Jang and coworkers

(1998) obtained a non-shared environment estimate of 52%, but the remaining 48% of the variance

was accounted for by additive genetic influences; the effects of the shared environment were

negligible. A similar pattern was obtained when they examined the non-pathological dissociation

scores. They further estimated that pathological and non-pathological dissociation scores shared

45% of the genetic and 34% of the environmental variance (Jang et al., 1998). The authors

suggested that pathological and non-pathological dissociation scores are influenced by a common

genetic predisposition to dissociate, but are differentiated by environmental factors. Although these

studies had a rather similar sample size of volunteer twins, one included high school students

(Waller and Ross, 1997) and the other one adolescents and adults (Jang et al., 1998). Contrary to

these studies, non-pathological dissociation was examined among child and adolescent twins by

using parents’ and teachers’ ratings of dissociative behaviours (Becker-Blease et al., 2004). The

ratings indicated moderate to substantial amounts of genetic and non-shared environmental variance

and negligible shared environmental variance. Longitudinal ratings showed that individual

differences in children’s non-pathological dissociation were moderately stable from year to year,

suggesting an individual tendency to dissociate independent of the influence of trauma (Becker-

Blease et al., 2004).

dissociation was associated with daily smoking (Tolmunen et al., 2007).

50

The role of childhood trauma, and a functional 44-bp insertion/deletion polymorphism in the

promoter region of the serotonin transporter (5-HTT) was investigated among patients with

obsessive-conpulsive disorder (OCD) (Lochner et al., 2007). The 5-HTT gene is one of the main

genes that control serotonergic function, and it has been hypothezised that this gene could play a

role in the development of OCD. Dissociation was measured with the DES (Bernstein and Putnam,

1986), and childhood traumatic experiences were assessed with the Childhood Trauma

Questionnaire (Bernstein et al., 1994). Subscales include emotional abuse, physical abuse, sexual

abuse, emotional neglect and physical neglect. The study analyses indicated that an interaction

between physical neglect and the S/S genotype of the 5-HTT gene significantly predicted

dissociation in patients with OCD (Lochner et al., 2007).

2.5.3. The relationship between psychological and somatoform dissociation

Studies using measurement scales for both psychological dissociation and somatoform

dissociation and various other outcome measures have been carried out in some non-clinical and

clinical samples, but no studies have been published on the general population. The correlation

between both forms of dissociation has been found to be significant (El-Hage et al., 2002; Nijenhuis

et al., 1999; ar et al., 2000), and researchers have argued for the diagnostic categorization of

conversion disorders (Nijenhuis, 2000; ar, 2006; Spitzer et al., 1998; Terzan et al., 1998). The

impact of trauma on psychological and somatoform dissociation has been an issue in most of these

studies (El-Hage et al., 2002; Nijenhuis et al., 1998c, 2003; Näring and Nijenhuis, 2005; ar et al.,

2004; Waller at al., 2000).

Considerable comorbidity with depression among patients with both conversion and dissociative

disorders has been found. The prevalence of reported childhood abuse was also high among these

patients ( ar et al., 2004; Terzan et al., 1998).

2.5.4. Stability of dissociative symptoms

Until now, no studies have been published on the stability of dissociative symptoms at the

population level. In clinical or selected non-clinical samples, DES scores have shown good

temporal stability over shorter periods of time. In small samples of dissociative disorder patients the

correlations have been as high as 0.93 over a period of 2-4 weeks (Frischholz et al., 1990, Van

Ijzendoorn and Schuengel, 1996). Among 26 normal subjects a test/retest reliability of 0.84 was

found over a period of 4-8 weeks (Bernstein and Putnam, 1986). In a study with a sample of 83

51

non-clinical female subjects the interval was one year, and Spearman’s correlation was 0.78

(Putnam et al., 1992).

In a study on a university student sample (n = 465) the stability of the DES scores and the

dissociative taxon membership were assessed with a two-month interval (Watson 2003). The

stability of the DES scores was good (r = 0.69), and the total DES score was 12.5 (SD 9.0) at time 1

and 12.8 (SD 10.5) at time 2. The prevalence of taxon membership (0.90 cut-off criterion) was

1.7% at time 1 and 3.0% at time 2. Altogether, 19 individuals (4.1% of the total sample) could be

classified as taxon members at either time 1 or 2, but only 3 (0.7%) met the criterion at both

assessments. According to these results, the dissociative taxon scores were only modestly stable and

they were substantially less stable than the continuous variables of dissociation (Watson, 2003).

52

3. Aims of the study

Previous general population studies on the prevalence of dissociation have mainly concerned the

psychological aspects of dissociation, and there have been no published data on the prevalence of

somatoform dissociation in the general population. There is controversy over whether psychological

and somatoform dissociation are manifestations of a common construct or different phenomena.

The stability of dissociative symptoms has previously only been investigated in small and/or

clinical samples and with relatively short follow-up periods.

The purpose of this study was to describe dissociation in the general population. The specific

aims of the present study were:

1) To determine the prevalence of pathological dissociation and mean scores of dissociation as well

as factors associated with pathological dissociation among Finnish general population adults.

Sociodemographic factors, depressive symptoms, suicidal ideation and alexithymia were

investigated (Study I).

2) To describe the prevalence of high somatoform dissociation and mean scores of somatoform

dissociation among Finnish general population adults. The impact of sociodemographic factors and

adverse childhood experiences was assessed (Study II).

3) To examine the relationship between psychological and somatoform dissociation in the Finnish

general population (Study III).

4) To describe the course of psychological dissociation during a three-year follow-up among

Finnish general population adults (Study IV).

53

4. Participants and methods

4.1. Study design

This study was part of a population-based longitudinal research project, the Kuopio Depression

(KUDEP) study. The main purpose of the general population arm of the survey was to investigate

the mental health of general population adults, its variations over a three-year follow-up and factors

associated with mental health.

The random general population survey included 3004 adult subjects aged 25-64 years selected

from the National Population Register. The sample was stratified for age, gender and district. All

study subjects were living in the province of Kuopio with a population of 251 000. Study

questionnaires were mailed for the first time in April 1998 accompanied by a letter in which the

study was described in detail. Participation was entirely voluntary. By returning the questionnaire

the respondents gave their informed consent. The data were collected at baseline in May-June 1998

(n = 2050), giving a response rate of 68.2%. Due to incomplete data, 49 subjects were excluded

from the analysis, and the final sample comprised 2001 subjects (Study I). The target measurement

scale for dissociation was the Dissociative Experiences Scale (DES).

In the second phase of the survey in May-June 1999 a second questionnaire was sent to 2945

subjects. Out of the 3004 subjects at baseline, 59 were excluded due to a changed and/or unknown

address (n = 45), refusal to participate (n = 10) or death (n = 4). A total of 1767 questionnaires were

returned, giving a response rate of 60.0%. Due to incomplete data, 28 subjects were excluded from

the analysis. Thus, the sample consisted of 1739 subjects (Study II). The measurement scale for

dissociation was the Somatoform Dissociation Questionnaire (SDQ-20).

The questionnaires for the follow-up were mailed in May-June 2001 to all those who responded

earlier either in 1998 or 1999 (n = 2223). On follow-up, 1618 subjects responded, giving a response

rate of 72.8% (53.9% of the baseline sample of 3004 subjects). After the exclusion of 33 subjects

with incomplete data, the sample comprised 1585 subjects (Study III). The questionnaire sent in

2001 included both the DES and the SDQ-20.

Furthermore, a total of 1534 subjects (51.1% of the baseline sample) responded both at baseline

in 1998 and on follow-up in 2001, but 37 subjects were excluded due to incomplete questionnaires.

The final sample therefore comprised 1497 subjects who responded in both phases (Study IV).

54

Figure 1. Formation of the study population.

4.2. Study population

4.2.1. Study I

The baseline sample comprised 2001 participants: 885 (44%) men and 1116 (56%) women.

More men (n = 572, 39.3%) than women (n = 382, 25.5%) were nonresponders (p < 0.001). The

nonresponding men were younger than the responding men (42.1 [SD 10.0] yrs vs. 44.8 [10.6] yrs,

p < 0.001), but no respective difference in age was found among women.

General population survey May-June 1998n = 3004

Excluded due to various reasons n = 59

May-June 1999 n = 2945

Responded at baseline 1998 n = 2050

Responded in 1999 n = 1767

Excluded due to incomplete data n = 28

Study II 1999 n = 1739

Study I 1998 n = 2001

Excluded due to incomplete data n = 49

Excluded due to incomplete data n = 37

Responded at baseline and follow-upn = 1534

Responded on follow-up 2001n = 1618

Excluded due to incomplete data n = 33

Study IV 2001 n = 1497

Study III 2001 n = 1585

55

4.2.2. Study II

The sample included 1739 participants: 742 (43%) men and 997 (57%) women. The mean age of

the respondents was higher than that of the nonrespondents (45.0 [SD 10.5] yrs vs. 41.9 [SD 10.6]

yrs, p < 0.001). More men than women did not participate (48.8% vs. 33.7%, p < 0.001). The

nonresponding men were significantly younger than the responding men (41.9 SD 10.4 vs. 45.6

SD 10.1 yrs; p < 0.001), but no such difference was found among women.

4.2.3. Study III

The sample consisted of 1585 subjects: 668 (41%) men and 917 (59%) women. The mean age of

the responders was higher than of the nonresponders (45.0 [SD 10.6] vs. 42.6 [SD 10.6] yrs, p <

0.001).

4.2.4. Study IV

The sample comprised 1497 subjects who responded both at baseline in 1998 and on follow-up

in 2001. There were 624 (42%) men and 873 (58%) women in this sample. On follow-up, more

men than women did not respond (29 vs. 22%, p < 0.001). Both the non-responding men and

women were younger then the respective respondents (in men: mean age 41.9 yrs [SD 10.4] vs.

46.1 yrs [SD 10.4], p < 0.001, and in women: 42.5 yrs, [SD 10.8] vs. 44.5 yrs, [SD 10.8],

p = 0.009). There was no statistically significant difference in the mean DES score at baseline

between the non-responding and responding men (8.5 [SD 9.1] vs. 7.7 [SD 8.0], p = n.s.), but the

mean DES score in the non-responding women was higher than in the responding women (9.7 [SD

10.6] vs. 7.8, [SD 7.6], p = 0.001).

56

Table 5. Sociodemographic characteristics of the subjects in studies I-IV.

Factors Study I Study II Study III Study IV

N = 2001 N = 1739 N = 1585 N = 1497

Female (%) 56 57 59 58

Age, mean (SD) 44.3 (10.7) 45.0 (10.5) 45.0 (10.6) 45.1 (10.6)

Married or cohabiting (%) 72 73 74 74

Living in an urban area (%) 75 74 75 74

Education 9 yrs (%) 84 85 84 84

4.3. Methods

All of the methods are described in this section, but not all were used in each individual study.

The exact methods for the separate studies are described in detail in the original publications.

The participants were questioned about their sociodemographic background (sex, age, marital

status and place of residence). In addition, a single question was asked to assess each of the

following factors: years of education ( nine years = high vs. < nine years = low); subjective

working ability (good vs. reduced or unable to work = reduced); financial situation (good or fairly

good = good vs. fairly poor or poor = poor); general health status (good or fairly good vs. fairly

poor or poor), and social support (adequate or fairly adequate vs. inadequate); alcohol consumption

(2-3 times/week or more = frequent vs. once a week or less = seldom); and current smoking (yes vs.

no).

4.3.1. The assessment of dissociation

Dissociative symptoms were assessed with the Dissociative Experiences Scale (DES) and the

Somatoform Dissociation Questionnaire (SDQ-20). The DES was included in study questionnaires

at baseline in 1998 and on follow-up in 2001, and the SDQ-20 was included in questionnaires in

1999 and on follow-up in 2001.

57

4.3.1.1. The Dissociative Experiences Scale (DES)

Dissociative symptoms were evaluated with the Finnish version (Tanskanen, 1997) of the

Dissociative Experiences Scale (DES). The Finnish version was translated first from English to

Finnish, and then back to English. Translation was carried out by an English language teacher at the

University of Kuopio. The scale is a 28-item, self-report instrument for the measurement of

dissociative experiences. The scale takes approximately ten minutes to complete and yields item,

subscale and total scores, which all range from 0 to 100. The individual’s total score is the mean of

the 28 items, and higher scores indicate greater levels of dissociation.

A Dissociative Experiences Scale Taxon (DES-T) with eight items from the DES has been

developed to more clearly distinguish the pathological component of dissociation (Waller and Ross,

1997). A cut-off score of 20 in the DES-T has been suggested to be optimal to distinguish general

population subjects with dissociative disorders (Waller and Ross, 1997; Ross et al., 2002). In Study

I, we selected this cut-off score for pathological dissociation to divide our sample into high

dissociators (DES-T 20) and low dissociators (DES-T < 20).

In study IV we used both the DES and its subscale DES-T in measuring dissociative symptoms

at baseline and on follow-up. A cut-off score of 20 in the Dissociative Experiences Scale was

selected to indicate high dissociation (Draijer and Boon, 1993; Steinberg et al., 1991). The sample

was categorized into low dissociators with DES scores below 20 and high dissociators with DES

scores of 20 or more. A statistical program was also used to calculate the dissociative taxon

membership probability on the basis of the DES-T scores. Subjects were classified as belonging to

the pathological dissociative taxon if their taxon probability exceeded 90% (Waller and Ross,

1997).

4.3.1.2. The Somatoform Dissociation Questionnaire (SDQ-20)

In study II the level of somatoform dissociation was estimated with a Finnish version of the

Somatoform Dissociation Questionnaire (SDQ-20) (Nijenhuis et al., 1996). The English version of

the SDQ-20 (Nijenhuis et al., 1996) was translated from English to Finnish by Antti Tanskanen

(M.D., Ph.D.), one of the researchers in the study. The SDQ-20 is a 20-item self-report

questionnaire in which an individual is asked to identify to what extent each statement is applicable

to him or her. The score corresponding to the response to each statement ranges from 1 to 5, and the

total score from 20 to 100. From previous research (Nijenhuis et al., 1999; ar et al., 2000) a cut-off

58

point of 30 in the SDQ was selected to categorize the sample into subjects with high somatoform

dissociation (SDQ 30) and subjects with low somatoform dissociation (SDQ <30).

Both the DES and the SDQ-20 were used in study III. A decile was used to compile equal groups

of subjects with the highest scores in the DES and the SDQ-20 to ensure a sufficiently large sample

size for analysis (Altman and Bland, 1994). In addition, those subjects with high scores in both DES

and SDQ-20 were separated from these two groups. Four groups were thus obtained from the total

sample: LBoth (low dissociation scores in both DES and SDQ-20), HDES (high DES and low

SDQ-20 scores), HSDQ (high SDQ-20 and low DES scores), and HBoth (high DES and high SDQ-

20 scores).

4.3.2. Depression

Depression has been conceptualized as a syndrome with a range of etiological factors and

comprising disparate symptoms, with disturbances of mood, thinking, sleep, appetite and motor

activity (DSM-IV, APA, 1994; ICD-10, WHO, 1992).

Depressive symptoms were assessed using the 21-item Beck Depression Inventory (BDI) (Beck

et al., 1961, 1988). In this study the sum of total scores was regarded as a continuous variable or

divided into four groups: 0-9 (normal mood), 10-18 (mild depression), 19-29 (moderate depression)

and 30-63 (severe depression). The three groups with scores ranging from 10-63, indicating

subjective symptoms of depression, were combined in multiple logistic regression analysis.

The prevalence of moderate to severe depression measured with the Beck Depression Inventory

was 11.7% in this general population sample (Hintikka et al., 2001a). The reliability of the BDI has

previously been demonstrated to be 0.89 (Cronbach’s alpha) in the same general population sample

(Honkalampi et al., 2000).

On one-year and three-year follow-up, questions were also asked concerning whether a

depressive episode had been diagnosed by a physician during the preceding 12 months, and whether

antidepressant medication had been used during the previous week. Some brand names of drugs

were given as examples.

4.3.3. Suicidal ideation

Suicidal ideation refers to cognitions that can vary from transient thoughts about the

worthlessness of life and death wishes to concrete plans for killing oneself and obsessive

preoccupation with self-destruction (Diekstra and Garnefski, 1995).

59

In this study, suicidal ideation was estimated with item nine of the BDI. The responses “I have

definite plans to commit suicide,” “I would kill myself if I had a chance” and “I feel I would be

better off dead” indicate the presence of suicidal ideation, and subjects choosing these options were

considered suicidal. The response “I have no thoughts of harming myself” indicates the absence of

suicidal ideation.

BDI item 9 has been previously used in screening for suicidal ideation in this general population

sample and has revealed the 12-month prevalence (14.7%) and incidence (4.6%) of suicidal ideation

(Hintikka et al., 2001a).

4.3.4. Alexithymia

The original definition given to alexithymia was the inability to recognize and verbalize

emotions (Sifneos, 1973). A poverty of imagination or of a fantasy world (Haviland and Reise,

1996), as well as a lack of positive emotions and a high prevalence of negative emotions have also

been considered to be characteristic of alexithymia (Taylor, 1994).

In the present study, alexithymia was assessed using the Finnish version (Joukamaa et al., 2001)

of the 20-item Toronto Alexithymia Scale (TAS-20) (Bagby et al., 1994). The total scores of the

TAS-20 were categorized according to the recommendations of Taylor and co-workers (1997); thus,

a score 61 indicated alexithymia, and 51 no alexithymia. Subjects with a TAS-20 score between

51 and 61 were categorized as intermediate. In multivariate analysis the intermediate group was

combined with the nonalexithymic group.

The prevalence of alexithymia in this general population sample has been demonstrated to be

12.8% in men and 8.2% in women (Honkalampi et al., 2000), and 10.0% in men and women

combined (Hintikka et al., 2001b). The reliability (Cronbach’s alpha) of TAS-20 in the same

general population sample was 0.86 (Honkalampi et al., 2000).

4.3.5. Adverse childhood experiences (ACEs)

Six questions were used to assess adverse childhood experiences (Haatainen et al., 2003). The

alternative responses and their classification are presented in parentheses after each question.

60

Poor relationship between parents

The relationship between parents was determined with the question: “What was the relationship

between your parents like in your childhood and adolescence?” (good, fairly good vs. don’t know,

fairly poor, poor and quarrelsome).

Unhappy childhood home

Happiness of childhood home was defined with the question: “Was your childhood home

happy?” (no vs. yes).

Hard parenting

Hard parenting was assessed with the question: “What was the parenting like?” (gentle, fairly

gentle vs. fairly hard, hard).

Physical punishment

Physical punishment (e.g. pulling one’s hair, spanking, birching) was investigated with the

question: “If you were physically punished under 15 years of age, by whom did it happen?” (yes, by

father, by mother, by both parents, by somebody else vs. no, I was not physically punished).

Domestic violence

Domestic violence was assessed with the question: “Have you suffered from domestic violence

directed to you in your childhood or adolescence?” (yes, physical violence, sexual violence, both

physical and sexual violence vs. no, I have not suffered from domestic violence).

Alcohol abuse at home

Alcohol abuse at home was assessed with the question: “Did anybody misuse or abuse alcohol in

your childhood home?” (yes, father, mother, both parents, somebody else vs. no, nobody).

In multiple logistic regression analysis, all the above-mentioned ACEs were studied

independently and by clustering them into three categories (none; one to three; four to six).

4.3.6. Statistical analysis

Data analyses were conducted using the statistical software package SPSS for Windows 11.0 or

11.5 (SPSS, Inc., Chigaco, IL). The results for the continuous variables were given as the mean,

SD, and statistical significance (p-value). A p-value of < 0.05 was considered statistically

significant in the analyses.

Relationships between the continuous variables were assessed with independent-samples t-test,

paired samples t-test, Mantel-Haenszel’s test for linear-by-linear associations, the Mann-Whitney

U-test or by analysis of variance (ANOVA) when appropriate, and Pearson’s (Studies I-III) or

Spearman’s (Study IV) bivariate correlation analysis.

61

The Pearson chi-squared test (with continuity Yates’ correction in Study I) or Fisher’s exact test

were used for categorical variables. Multiple logistic regression analysis (method: enter) was

performed to determine risk factors (OR with 95% CI) for dissociation.

To evaluate the reliability of the measurement scales for dissociation (DES and SDQ-20), a test

of internal consistency (Cronbach’s -coefficient) was used in all studies I-IV. Bayesien probability

scores were calculated for the dissociative taxon membership using the SAS program scheme

and. All statistical tests

(Waller and Ross, 1997) that was converted to a SPSS program comm

were two-tailed.

62

5. Results

5.1. Pathological dissociation (Study I)

5.1.1. The prevalence of pathological dissociation and mean scores of the DES in the general

population

The prevalence of pathological dissociation (DES-T 20) in the general population was 3.4%,

and there was no statistically significant difference between men (3.6%) and women (3.2%). The

mean total DES score for the entire sample was 8.0 (SD 8.1). The mean total DES score was lower

in men than women (7.8 vs. 8.2, p = 0.034), and it declined slightly but not significantly with age.

5.1.2. Factors associated with pathological dissociation

Depressive symptoms, alexithymia and suicidality had a strong association with pathological

dissociation. Single, divorced or widowed male subjects were quite often high dissociators. A poor

financial situation was associated with pathological dissociation, but the association was

statistically significant only in men. In subjects with a reduced working ability the prevalence of

high dissociators was higher than in those with a good working ability in both genders. Frequent

alcohol consumption was associated with pathological dissociation in women and current smoking

in men.

Multiple logistic regression analysis was performed on four models, each including one

psychiatric symptom variable and the sociodemographic variables, and one model in which all three

psychiatric symptom variables were included. In Model 1, pathological dissociation was

significantly associated with depression. Subjects with depression had a nearly nine-fold greater

risk of pathological dissociation compared with subjects with a normal mood. In Model 2, the

likelihood of pathological dissociation was more than seven-fold greater in alexithymic subjects

compared with subjects without alexithymia. In Model 3, the odds of pathological dissociation were

over four-fold greater among suicidal subjects compared with nonsuicidal subjects. In Model 4, all

three psychiatric symptom variables were included in the same multiple logistic regression model to

assess the significant independent relationships with pathological dissociation. The odds ratios of

pathological dissociation remained statistically significant in depressive (AOR 3.85 [95%CI 1.88-

7.90]), alexithymic (AOR 4.01 [95%CI 2.15-7.49]) and suicidal (AOR 2.19 [95%CI 1.16-4.13])

63

subjects. Frequent alcohol consumption had a significant association with pathological dissociation

in all models.

5.2. Somatoform dissociation (Study II)

5.2.1. The prevalence of somatoform dissociation and the mean scores of the SDQ-20 in the

general population

The prevalence of high somatoform dissociation (SDQ-20 30) was 9.4% in the general

population. The prevalence of somatoform dissociation was higher among men than women (11.1%

vs. 8.2%, p = 0.047). The mean SDQ score was 23.3 (SD 6.1) among the total sample, and it was

higher in men than in women (23.8 [SD 6.9] vs. 22.9 [SD 5.3], p = 0.002). The reliability alpha

coefficient of SDQ-20 was 0.89 in this study.

5.2.2. Sociodemographic variables

The prevalence of high somatoform dissociation increased with age, low education,

unemployment, a reduced working ability and a poor financial situation. In multiple logistic

regression models, the odds for high somatoform dissociation were increased with a reduced

working ability (AOR 3.96 [95% CI 2.59-6.03], p < 0.001) and a poor financial situation (AOR

2.26 [95% CI 1.54-3.32], p < 0.001) among the participants.

5.2.3. Adverse childhood experiences (ACEs)

High somatoform dissociation was more prevalent among women with different adverse

childhood experiences, except for a poor relationship between the parents. Among men, high

somatoform dissociation was associated with a poor relationship between the parents, an unhappy

childhood home and physical punishment.

In multiple logistic regression models, physical punishment (AOR 2.26 [95% CI 1.46-3.48],

p < 0.001) was associated with high somatoform dissociation. There were some differences between

men and women: a poor relationship between the parents (AOR 2.18 [95% CI 1.08-4.42],

p < 0.001) increased the odds of high somatoform dissociation among men, and alcohol abuse in

their childhood home (AOR 1.77 [95% CI 1.03-3.03], p < 0.001) among women.

64

The adjusted relative risk (AOR) of high somatoform dissociation was 2.03 (95% CI 0.83-4.95,

p = n.s.) with 1-3 ACEs and 3.05 (95% CI 1.11-3.36, p = 0.030) with 4-6 ACEs among men, while

among women the adjusted relative risk of high somatoform dissociation increased to 2.65 (95% CI

1.16-6.04, p = 0.021) with 1-3 ACEs and 5.43 (95% CI 2.22-13.28, p < 0.001) with 4-6 ACEs.

The prevalence of high somatoform dissociation increased linearly with an increasing number of

ACEs in both genders. It increased from 5.1% to 19.4% among men (p = 0.001), and from 3.4% to

16.6% (p < 0.001) among women with cumulative ACEs.

5.3. The relationship between psychological and somatoform dissociation (Study III)

In study III, subjects with both high somatoform dissociation and psychological dissociation

(HBoth) were compared with subjects with either high psychological dissociation (HDES) or with

high somatoform dissociation (HSDQ). The HBoth subjects had higher mean DES (HBoth: 24.9

SD 11.9 vs. HDES: 17.3 SD 6.2 , p < 0.001, and HSDQ: 6.3 SD 2.9 , p < 0.001) and SDQ-20

(HBoth: 34.5 SD 9.4 vs. HSDQ: 28.2 SD 3.0 , p < 0.001, and HDES: 21.9 SD 1.8 , p < 0.001)

scores than subjects in the other groups. They more often reported depressive symptoms, suicidal

thoughts, a reduced working ability, a poor financial situation, poor general health and inadequate

social support compared with subjects in the other groups. The HBoth subjects were also more

frequently single, divorced or widowed compared with the HSDQ subjects. The reliability alpha

coefficients of the DES and the SDQ-20 in this sample were 0.94 and 0.83, respectively. The

Pearson’s correlation between the DES and SDQ-20 scores was 0.60.

Three multiple logistic regression models were used to identify factors that were associated with

HDES, HSDQ and HBoth compared with the LBoth group. Depressive symptoms (AOR 1.99 [95%

CI 1.07-3.72]), suicidality (AOR 2.26 [95% CI 1.14-4.46]) and a younger age (AOR 0.97 [95% CI

0.95-1.00]) were associated with HDES. Factors associated with HSDQ were suicidality (AOR 2.68

[95% CI 1.38-5.21]) and a reduced working ability (AOR 2.20 [95% CI 1.21-4.00]). Depressive

symptoms (AOR 9.19 [95% CI 3.96-21.32]), suicidality (AOR 3.05 [95% CI 1.56-5.96]), a reduced

working ability (AOR 2.59 [95% CI 1.08-6.20]), a younger age (AOR 0.96 [95% CI 0.93-0.99]),

and being single, divorced or widowed (AOR 1.99 [95% CI 1.09-3.63]) were associated with

HBoth.

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5.4. Course of dissociation in the general population (Study IV)

5.4.1. Stability of psychological dissociative symptoms

The majority (98%, n = 1371) of subjects with low dissociation at baseline (n = 1399) were also

low dissociators on follow-up. In 28 subjects (2% of baseline low dissociators) the DES score

increased above the cut-off score (new cases). At the same time, the DES score of 70 subjects (71%

of the 98 baseline high dissociators) decreased below the cut-off score (recovered cases). Twenty-

eight subjects were constantly high dissociators (stable cases) (29% of the 98 high dissociators at

baseline). Statistically significant differences were detected between the groups for four background

factors: age, working ability, subjective general health and smoking.

With a 0.90 probability cut-off score, 28 (2%, n = 1463) dissociative taxon members could be

identified at baseline and 15 (1%) on follow-up, but only four (0.3%) subjects met the criteria in

both assessments.

There was no statistically significant change in the mean DES (35.9 [SD 13.2] vs. 32.0 [SD

10.0], p = n.s.) or DES-T (27.4 [SD 16.4] vs. 24.0 [SD 11.3], p = n.s.) score between baseline and

follow-up in stable cases. However, the changes in DES and the DES-T scores were significant

among new (DES: 9.0 [SD 4.8] vs. 29.7 [SD 11.0], p < 0.001; DES-T: 4.4 [SD 3.3.] vs. 22.9 [SD

14.3], p < 0.001) and recovered (DES: 28.4 [SD 7.8] vs. 9.9 [SD 5.5], p < 0.001; DES-T: 19.0 [SD

11.1] vs. 4.6 [SD 4.4], p < 0.001) cases.

5.4.2. Associations between dissociation, depressive symptoms and suicidal ideation

There was no significant change among recovered cases in the mean BDI score (12.4 [SD 9.8]

vs. 10.2 [SD 8.4], p = n.s.) or the prevalence of suicidal ideation (22.9% vs. 20.0%, p = n.s.) during

the follow-up period. However, in new cases the mean BDI score (9.2 [SD 9.6] vs. 16.7 [SD 14.3],

p = 0.011) and the prevalence of suicidal ideation (21.4% vs. 35.7%, p = 0.013) increased

significantly during the follow-up. In stable cases, no significant difference was recorded between

any of the variables, the mean BDI score was at a high level (15.8 [SD 10.2] vs. 18.3 [SD 11.7],

p = n.s.), and half of the cases had suicidal thoughts (53.8% vs. 46.4%, p = n.s.). In low

dissociators, significant declines were observed in the mean DES score (6.1 [SD 4.3] vs. 4.4 [SD

3.7], p < 0.001) and the prevalence of suicidal ideation (9.0% vs. 6.9%, p < 0.001), but there was no

change in the mean BDI scores during the follow-up (4.8 [SD 5.7] vs. 4.9 [SD 6.2], p = n.s.).

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In the group of stable cases there was an increase in the proportion taking antidepressant

medication (15.4% vs. 26.9%, p = 0.047), but no change in the diagnosis of depression (34.6% vs.

38.5%, p = n.s.) between baseline and follow-up. Among recovered cases the prevalence of a

diagnosis of depression (13.1% vs. 9.8%, p = 0.002) and the use of antidepressant medication

(14.8% vs. 11.5%, p < 0.001) significantly declined, but among the new cases the diagnosis of

depression (16.7% vs. 37.5%, p = 0.012) was made more frequently, and they more often used

medication for depression (20.8% vs. 29.2%, p = 0.014) after the follow-up period.

Stable high dissociation was associated with an increase in the BDI score (AOR 1.08 [95% CI

1.02-1.14], p = 0.008) and with suicidal ideation (AOR 6.39 [95% CI 2.49-12.39], p < 0.001), a

younger age (AOR 0.93 [95% CI 0.88-0.98], p = 0.004), a reduced working ability (AOR 4.76

[95% CI 1.56-14.48], p = 0.006) and smoking (AOR 2.83 [95% CI 1.17-6.86], p = 0.021) at

baseline. Becoming a new case was predicted by an increase in the BDI score (AOR 1.13 [95% CI

1.08-1.18], p < 0.001), and by a younger age (AOR 0.94 [95% CI 0.89-0.98], p = 0.011), and a

reduced working ability (AOR 4.66 [95% CI 1.62-13.39], p = 0.004) at baseline. No factor was

found to explain the recovery from dissociation in this model. However, when we compared stable

with recovered cases, recovery from high dissociation was predicted by a decline in the BDI score

during the follow-up (AOR 0.92 [95% CI 0.87-0.98], p = 0.01) and by having no suicidal thoughts

(AOR 0.19 [95% CI 0.51-0.70], p = 0.012), an older age (AOR 1.10 [95% CI 1.02-1.18], p = 0.01),

and a good working ability (AOR 0.18 [95% CI 0.03-0.94], p = 0.041) at baseline.

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6. Discussion

6.1. Prevalence of dissociation in the general population

The prevalence of pathological dissociation in Finland (3.4%) was at the same level as in studies

on the North American general population with the same cut-off score of 20 in the DES-T (Seedat

et al., 2003). The mean DES-T score in our study (3.8 [SD 6.9]) was also similar to that reported by

Seedat and coworkers (3.5 [SD 8.6]), but higher than the mean DES-T score in a recent non-clinical

study in Germany (2.3 [SD 4.2]) (Spitzer et al., 2006). There have been no previous published

studies on the prevalence of pathological dissociation in European general population samples.

Total dissociation (DES and DIS-Q) scores or the estimated prevalence of psychological

dissociation have tended to be lower in Europe than in North America (Akyüz et al., 1999; Ross et

al., 1990; Spitzer et al., 2006; Vanderlinden et al., 1991, 1993). However, in a Turkish general

population of female participants the prevalence of high dissociation was as high as 15.9% (total

DES score >20), and the mean DES score was 11.8 (SD 10.2 (Akyüz et al., 2005). By contrast, the

total DES score was as low as 2.6 (SD 4.3) in a Chinese non-clinical population of factory workers

(Xiao et al., 2006a, b).

The prevalence of dissociative taxon membership in our follow-up study was lower (2% at

baseline and 1% on follow-up) than in North America (Waller et al., 1997), but considerably higher

than in Germany (Spitzer et al., 2006) or China (Xiao et al., 2006a, b). The non-clinical samples

were smaller (Spitzer et al., 2006; Xiao et al., 2006a, b) than our general population sample, and the

generalization of the results of selected samples has more limitations than with a general population

sample. According to the predictions of the trauma model of dissociation, (1) pathological

dissociation occurs in all cultures, and (2) within any given culture, it is more frequent in samples

with higher levels of childhood trauma (Xiao et al., 2006 a). The sociocognitive model, on the other

hand, predicts that pathological dissociation is unrelated to childhood trauma and arises from one of

two sources: (1) expectations and demand characteristics imposed by mental health professionals,

and (2) significant popular knowledge of pathological dissociation, especially dissociative identity

disorder, which influences susceptible individuals to role enact the expected symptoms and

behaviours (Xiao et al., 2006a, Spanos, 1994). In central-eastern Finland, almost no public

knowledge exists concerning dissociative disorders, the possibility of role demands or iatrogenic

suggestion. However, the prevalence of pathological dissociation was at the same level as in North

America, where dissociative symptoms and especially the dissociative identity disorder (DID) have

gained more widespread public knowledge. The high prevalence of dissociative experiences among

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women from rural districts of Turkey (Aküyz et al., 2005) with a concomitant high prevalence of

childhood abuse in that sample does not support the sociocognitive model of dissociation, either.

The socio-cognitive model has gained little empirical support (Dell, 2006b; Gleaves, 1996).

To my best knowledge, no previous studies have examined the prevalence of somatoform

dissociation in a general or non-clinical population. The prevalence of high somatoform

dissociation in our study was quite high (9.4%), suggesting that somatoform dissociative symptoms

are common at the population level. The mean SDQ-20 score in our study (23.3 [SD 6.1]) was at

the same level as in a random Dutch non-clinical sample (23.2 [SD 5.0]; Näring and Nijenhuis,

2005), but lower than in a Turkish non-clinical sample ( ar et al., 2000), in which the mean SDQ-

20 score was 27.4 (SD 8.2).

6.2. Factors associated with dissociation

6.2.1. Age

Pathological dissociation was not associated with age in our Study I. In addition, there was no

statistically significant association between age and the total DES score. These results differ from

previous studies, where DES (Ross et al., 1990) or DES-T (Seedat et al., 2003) scores have declined

with age. The age range in our study did not include subjects from eighteen to twenty-five years of

age, and this might influence the associations with age, as younger subjects have scored

significantly higher in the DES (Ross et al., 1990).

The prevalence of high somatoform dissociation increased with age in our Study II, which is

contrary to previous studies in which age did not affect the SDQ-20 scores (Nijenhuis et al., 1996,

1998a). In a Turkish patient study ( ar et al., 2000) a weak positive correlation between high

somatoform dissociation and older age was found. However, the previous studies have been

performed on small, heterogeneous samples, and no studies at a population level have been

published. There is a possibility that older, less educated subjects could report more frequent

somatic symptoms, and this might also have influenced our SDQ-20 scores, although it has been

shown that somatoform dissociation cannot be equated with a tendency to report physical

complaints (Nijenhuis et al., 1999). In the Dutch study, however, due to the male/female ratio and

the mean ages in the diagnostic groups, older male subjects were poorly represented.

In Study III, subjects with high somatoform dissociation were significantly older than subjects

with high psychological dissociation. However, a younger age predicted simultaneous high

somatoform and high psychological dissociation (HBoth), and these subjects also had the highest

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scores in both DES and SDQ-20, indicating the highest levels of dissociative symptoms. In the

follow-up study (Study IV), a younger age also predicted stable high dissociation and the risk of

becoming a new case in the follow-up period.

6.2.2. Sex

The total DES score was higher in women than men, but gender did not affect the DES-T scores

in Study I. Our results with the DES subscales were similar to a study with a large, selected German

sample (Spitzer et al., 2003): men scored higher in the amnesia subscale compared with women,

and there was no gender difference in the DES-T scores. The gender difference in the amnesia

subscale was also found in a Dutch population sample (Vanderlinden et al., 1991). As dissociative

amnesia represents a diagnostic criterion for posttraumatic stress disorder (PTSD), it may be that

men and women react differently to traumatizing events, and there may be gender differences in the

storage, consolidation and retrieval of traumatic memories (Spitzer et al., 2003). The total DES

score, the scores for the absorption and imaginative involvement factor, and the nonpathological

part of the DES were higher in women than men in our study. Our results suggest that the

pathological aspects of dissociative experiences are equally common in both genders, but the

nonpathological dissociative symptoms are more prevalent among women.

Men scored significantly higher than women in the Somatoform Dissociation Questionnaire,

which is contrary to previous studies in Dutch samples, where gender did not affect the SDQ-20

scores (Nijenhuis et al., 1996, 1998a). Young men were the least likely to respond to our

questionnaires, and this might also have influenced the results obtained for the DES, DES-T, and

SDQ-20 scores, but in different directions due to the different associations with age.

6.2.3. Socioeconomic and marital status

Apart from the negative association with age, sociodemographic factors have not generally been

associated with high psychological dissociation (Ross et al., 1990). Pathological dissociation had

significant bivariate associations with several factors in Study I, but in logistic regression analysis

only subjective work disability had a significant relationship with pathological dissociation.

High somatoform dissociation was associated with a low educational level, reduced working

ability or poor socio-economic status, and a similar trend compared with our results was found in a

Turkish patient study ( ar et al., 2000). In Study III, subjects with both high psychological and high

somatoform dissociation (HBoth) had considerable adversities in their health, working ability and

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financial and social situation compared to other groups. The HBoth subjects probably had a cluster

of dissociative symptoms typical of either complex post-traumatic stress disorder or dissociative

disorders ( ar et al., 2004; Van der Hart et al., 2006), which significantly affected their lives.

Reduced working ability also strongly predicted stable high dissociation in the follow-up study,

which further supports the impact of dissociative pathology on the individual’s daily functional

capacity.

6.2.4. Substance use (alcohol and tobacco)

Although frequent alcohol consumption had a significant relationship with pathological

dissociation in the cross-sectional study (Study I), it was not associated with stable high dissociation

in the follow-up study (Study IV). However, smoking was common among stable high dissociators,

and there was an almost three times greater risk for being a stable high dissociator among baseline

smokers compared to nonsmokers. Although rates of smoking among populations with psychiatric

disorders are more than twice as high as among the general population, the mechanism of this

relationship is not yet clear, and there have been virtually no published studies on the association

between smoking and dissociation. In a study with male prison inmates, self-cutting inmates had

begun smoking and other substance abuse earlier than non-cutters and also scored higher in the

Adolescent Dissociation Experiences Scale (A-DES) (Matsumoto et al., 2005). Post-trauma mental

health disturbances such as post-traumatic stress disorder (PTSD) have been associated with

increased smoking (Breslau et al., 2003), either by starting to smoke or an increase of tobacco use.

In addition, the effect of smoking on PTSD symptoms has been examined (Buckley et al., 2007),

and smoking has been found to be an independent risk factor for severe anxiety and hostility

symptoms and subsequent PTSD among adult disaster victims and for anxiety symptoms among

adult people who are confronted with stressful life events (Van der Velden et al., 2007). Smoking

may also be a coping mechanism to reduce distress caused by traumatic or stressful events.

However, in our study IV, no trauma variables were included, so no definite conclusions about the

interesting association between smoking and stable high dissociation can yet be drawn.

6.3. Comorbidity between dissociation, depressive symptoms and suicidal ideation

In Studies I, III and IV a strong relationship between high levels of dissociation, depressive

symptoms and suicidal ideation was observed, supporting earlier findings that dissociative

pathology is linked with substantial comorbidity (Mulder et al., 1998; Nijenhuis et al., 2003; ar et

71

al., 2004; Saxe et al., 1993). In cross-sectional Study I the risk of pathological dissociation was

increased almost nine-fold with current depressive symptoms and four-fold with suicidal ideation.

The association between dissociation and depressive symptoms in HBoth subjects was striking:

80% of them had BDI scores suggestive of current depression and half of them had suicidal

thoughts (Study III). The relationship between dissociation, depressive symptoms and suicidal

ideation was as significant in the follow-up study (Study IV) as in the cross-sectional studies

(Studies I and III). Stable cases had long-lasting high mean BDI scores, half of them had persistent

suicidal ideation, and the frequency of antidepressant medication use among them was high and

even increased during the follow-up period. The dissociative symptoms probably remained

unrecognized, because dissociative disorders have rarely been diagnosed properly (Foote et al.,

2006; Lipsanen et al., 2004a). For example, in 2000 there were 99 inpatients in Finland who had

been diagnosed as having a dissociative disorder (3‰ of all inpatients, total n = 32669) (National

Research and Development Centre for Welfare and Health, 2001), while the estimated prevalence

of dissociative disorders in inpatients has ranged from 4-21% (Foote et al., 2006; Ross et al., 1991).

6.3.1. Comorbidity between dissociative experiences and depressive symptoms

Pathological dissociators have been found among patients with affective, anxiety and

somatoform as well as personality disorders, and they have had more psychopathological

impairment than non-pathological dissociators (Spitzer et al., 2006). An explanation for the

comorbidity of dissociation might be adaptation to stress and the consequences of experiencing

traumatic events (Anderson et al., 1993; Ellason et al., 1996; Francia-Martinez et al., 2003; Van der

Kolk et al., 1996; Yargic et al., 1998). In the general population the relationships between high

dissociation, psychiatric comorbidity and childhood abuse have been examined with somewhat

controversial results (Akyüz et al., 1999; Mulder et al., 1998; ar et al., 2007).

In the Turkish general population, no statistically significant association between high

dissociation (DES >17) and major depression (or any other diagnosis except dissociative disorders)

was found, and only childhood neglect and all types of childhood abuse combined were associated

with high dissociation (Akyüz et al., 1999). The major limitation in that study was a significant loss

of participants in the interviewing process, and small eventual study groups (Akyüz et al., 1999). A

more recent epidemiological study in the same region of Turkey comprised only female subjects

( ar et al., 2007), and lifetime major depressive disorder was the most prevalent comorbid diagnosis

among the participants with dissociative disorders. Other diagnostic groups associated with a

diagnosis of dissociative disorders were somatization disorders, borderline personality disorder and

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PTSD. Of the abuse variables, sexual abuse, physical neglect and emotional abuse were associated

with a diagnosis of a dissociative disorder ( ar et al., 2007).

High dissociation (modified version of the DES and interviews) was associated with both

childhood abuse and current psychiatric illness (mood, anxiety, substance use disorders and PTSD)

in the general population of New Zealand (Mulder et al., 1998). However, in logistic regression

analysis only physical abuse and current psychiatric DSM-III-R disorder were associated with high

dissociation. Sexual abuse was indirectly associated with high dissociation: it was related to both

physical abuse and the current mental state. A direct causal relationship between childhood sexual

abuse and dissociation was argued, but the comorbidity of high dissociation was evident (Mulder et

al., 1998). A recent study on a non-clinical sample of young adults also showed that combined

exposure to parental verbal aggression and witnessing domestic violence was associated with an

extraordinarily large effects size on dissociation, and the association was even stronger than with

familiar sexual abuse. The effect sizes were almost as strong on depression (Teicher et al., 2006).

The differing results reported above may reflect cultural differences, differences in study design

and procedure, or the definitions of high dissociation and childhood abuse. These studies also

illustrate the difficulties in using retrospective reports of childhood traumatisation (Akyüz et al.,

1999; Mulder et al., 1998; Vanderlinden et al., 1993), but it seems that there is reliable evidence of

associations between dissociation, depression and childhood traumatization. Our studies did not

include diagnostic procedures or trauma variables, but they demonstrated significant associations

between high dissociation, depressive symptoms and suicidality cross-sectionally and on follow-up.

Patients with dissociative disorders have many concurrent comorbid diagnoses, because the

diagnostic criteria for these categories do not exclude each other. On the other hand, the excessive

descriptive comorbidity might be reflecting different facets of a single multifaceted psychiatric

condition, the clinical expression of adult psychopathology related to childhood trauma (Herman,

1992). Patients with dissociatiative disorders report the highest frequency of childhood trauma

among all psychiatric categories (Ross et al., 1989), and have extensive psychiatric comorbidity in

both DSM axels (Ellason et al., 1996). Particularly trauma that occurs early in the life cycle can lead

to complex characterological adaptations, as well as disturbed regulation of affective arousal (poor

impulse control, self-mutilating behaviour), an impaired capacity for cognitive integration of

experience (as in dissociation), and impairment in the capacity to differentiate relevant from

irrelevant information, which occurs in the misinterpretation of somatic sensations (Van der Kolk et

al., 1996).

Because dissociation has been difficult to define and disentangle from other psychological

constructs, one perspective opposing the trauma theory has suggested that dissociative phenomena

73

are non-specific and can be found in a variety of other disorders (Fahy 1988; Fahy et al., 1989). One

study has addressed this issue with multiple measures of dissociative experiences and a variety of

theoretically-related constructs (antisocial, borderline, PTSD, depression, and anxiety) in a sample

of 225 college students. Similar difficulties with discriminant validity were found in all

measurement scales, not just with the measurement scales of dissociation. The data supported the

construct-related validity of three dissociation instruments, and offered moderate evidence that

although dissociation was highly associated with other constructs, it could be seen as a distinct,

valid and reliable phenomenon in a non-clinical sample (Gleaves et al., 2000).

6.3.2 The relationship between psychological and somatoform dissociation

The relationship between psychological and somatoform dissociation has not been studied in the

general population, but comorbidity among patients with concomitant conversion and dissociative

disorders have been examined in two studies ( ar et al., 2004; Terzan et al., 1998). ar and

coworkers (2004) included both the SDQ-20 and DIS-Q in their study design, while the other study

(Terzan et al., 1998) included the DES, as well as diagnostic interviews for dissociative disorders

and comorbid symptomatology. In both studies a simultaneous diagnosis of a conversion disorder

and dissociative disorder meant more severe psychopathology compared to patients with mere

conversion disorder: high comorbidity with depression ( ar et al., 2004; Terzan et al., 1998) and

more suicide attempts and self-mutilative behaviour ( ar et al., 2004). Our results in Study III are in

agreement with these studies, indicating greater psychopathological impairment among HBoth

subjects compared to other groups.

6.3.3. The relationship between dissociation and suicidal ideation

Childhood trauma and neglect were found to be associated with suicide attempts and self-

mutilation in a sample of the female general population in Turkey (Aküyz et al., 2005). In that

study, physical neglect and sexual abuse of different childhood trauma types were associated with

higher DES scores among the participants. Furthermore, dissociation had a mediating role between

childhood sexual abuse and a variety of mental health outcomes, including suicidality, sexual

aggression and self-mutilation among adolescents (Kisiel and Lyons, 2001).

Dissociation is a frequent concomitant of self-injury. Many patients report feeling numb and

“dead” prior to harming themselves (Pattison and Kahan, 1983). They often claim not to experience

pain during self-injury and report a sense of relief afterwards (Favazza and Conterio, 1988; Pattison

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and Kahan, 1983). Episodes of self-mutilation often follow feelings of disappointment or

abandonment (Favazza and Conterio, 1989). In contrast to self-injury, suicide attempts are reported

not to provide relief, to be repeated less frequently, and to have less communicative value (Pattison

and Kahan, 1983). Persistent suicidal ideation has been demonstrated to be associated with a

markedly increased probability of planned suicide attempts at the population level (Kessler et al.,

1999). In a 12-month follow-up study on the Finnish general population, suicidal ideation was

observed to be common and persistent (Hintikka et al., 2001b).

Apart from the high prevalence of persistent suicidal ideation in stable high dissociators in our

Study IV, the frequency of suicidal ideation remained at 20% in the recovered cases despite the

significant decline in the dissociation scores during the three-year follow-up period. These results

suggest that suicidal ideation was a more enduring feature in some subjects in our follow-up study,

who might at the same time experience more state-like dissociative symptoms. The recovered cases

received a diagnosis of depression and used antidepressants less frequently at the three-year follow-

up point. The decline in the DES scores could be a result of a positive treatment outcome in some

individual subjects, because psychiatric treatment has been shown to reduce depressive symptoms

in dissociative identity disorder patients (DID) (Coons and Bowman, 2001; Ellason and Ross,

1997). Suicide ideation was not assessed in these studies. There was a significant reduction in

diagnosed depression in recovered cases over the follow-up, but we consider it unlikely that this

could be the cause of the recovery from dissociation in all 70 cases. The factors associated with

recovery from dissociation require further research.

6.4. The relationship between dissociation and alexithymia

Contradictory views concerning the associations between alexithymia and dissociation have been

reported in different clinical (Grabe et al., 2000, Tutkun et al., 2004; Wise et al., 2000) and non-

clinical (Elzinga et al., 2002; Irwin and Melbin-Helberg, 1997; Modestin et al., 2002) samples, but

to my knowledge no reports have been published on general population samples. In our Study I,

alexithymia had a statistically significant association with pathological dissociation in both genders,

and the risk for pathological dissociation was greater in alexithymic subjects compared with non-

alexithymic subjects even after adjusting for depression and several other covariates in logistic

regression analysis. However, we did not differentiate between the three factors of alexithymia or

investigate their associations with pathological dissociation. Our results therefore provide no further

evidence concerning whether the factor ‘difficulty identifying or describing feelings’ was associated

75

with pathological dissociation, as has previously been postulated (Elzinga et al., 2002; Irwin and

Melbin-Helberg, 1997; Modestin et al., 2002).

Grabe and coworkers (2000) found that alexithymia predicted pathological dissociation, but their

article did not explicitly mention how dissociation was categorized into ‘pathological’ and ‘non-

pathological’ forms or how they calculated their total dissociation scores. However, they suggested

that pre-existing alexithymic features might modulate the individual stress response to distressing or

traumatic experiences in a dysfunctional way, thus increasing the risk for pathological dissociation.

In a study including the DES (DES-T) and the SDQ-20, no associations between pathological

dissociation and alexithymia were found after controlling for age, gender and general

psychopathology, but somatoform dissociation remained significantly related to alexithymia

(Clayton, 2004).

According to Nemiah (2000), in the alexithymic individual, stress-induced arousal undergoes no

psychic elaboration and is directly transformed into a somatic dysfunction, but psychic conversion

symbolically represents the original stressful situation. Despite the differences, both models of

symptom formation are psychological in nature. Both use a psychological model that perceives

symptoms as the end result of stress-induced internal psychic arousal in the form of peripheral

somatic manifestations. Alexithymia and dissociation may both be viewed as a defence against

over-whelming experiences. In this context, alexithymia is termed secondary alexithymia to

differentiate the construct from primary alexithymia, which has been assumed to be genetic or

biological in origin (Freyberger, 1977).

Other explanations for the association between dissociation and alexithymia have been proposed.

Irwin (1997) stated that people with dissociative tendencies have a ‘normal’ affective vocabulary

but have difficulty utilizing this vocabulary to depict their own affective states. This suggests that

the verbal processing system tends to be dissociated from affective processes, additionally

indicating that alexithymia involves the inability to link personal states to emotional words

(‘difficulty identifying and describing feelings’). The isolation of painful affects in dissociation and

secondary alexithymia states, possibly potentiated with depressed mood, may be the common

element. However, the contradictory results from studies that found no association between

dissociation and alexithymia (Tutkun et al., 2004), and associations weakened by confounding

general psychopathology (Wise et al., 2000), have indicated that dissociation fundamentally differs

from alexithymia in that dissociation involves a change of one’s self, whereas alexithymia reflects a

cognitive state of externally-oriented thinking with an inability to identify and report discrete

emotions (Wise et al., 2000). The relationship between dissociation and alexithymia merits further

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study, taking into account possible gender differences, the factor structure of alexithymia and

possible associations with somatoform dissociation (Clayton, 2004).

6.5. The impact of adverse childhood experiences (ACEs) on somatoform dissociation

In addition to the associations between single adverse childhood experiences (ACEs) and

somatoform dissociation, we measured the impact of multiple ACEs and found a strong, graded

relationship between high somatoform dissociation and an increasing number of ACEs in both

genders. In a previous study the conversion disorder patients who reported multiple types of

childhood traumatization scored significantly higher in the SDQ-20 than conversion disorder

patients with a single type of traumatization (Roelofs et al., 2002). As a large ACE study (Dube et

al., 2001; Felitti et al., 1998) has shown, simultaneously considering the impact of multiple

experiences is important, because ACEs are strongly interrelated and also related to poor physical

and mental health. A review article in which adult retrospective reports of more than one form of

child maltreatment were assessed also showed that the maltreatment types do not occur

independently, and that a significant proportion of individuals experience not just repeated episodes

of one type of maltreatment, but are likely to be victims of other forms of abuse and neglect

(Higgins and McCabe, 2001). The impact of parental verbal aggression on dissociation and limbic

irritability was assessed in a recent study on a non-clinical population of late adolescents (Teicher et

al., 2006). While verbal aggression was associated with moderate to large effects, multiple forms of

abuse were associated with very large effect sizes, with an effect size that was often greater than the

component sum (Teicher et al., 2006).

We found a strong association between somatoform dissociation and physical punishment among

both men and women. Domestic violence, including both sexual and physical violence in

childhood, had a bivariate association with high somatoform dissociation, but the association was

not significant in multiple logistic regression in our population-based sample. It has been suggested

that somatoform dissociation would be more clearly associated with physical abuse where there is a

threat of inescapable physical injury, and somatoform dissociation could be understood as a set of

adaptive psychophysiological responses to trauma (Waller et al., 2000). The frequency of sexual

abuse reported by both genders in our study was low, which gives reason to assume that the results

reflect under-reporting. The other limitation in this issue may be the possibility of recall bias. It

would have been more justifiable to use validated questionnaires (Bernstein et al., 1994; Nijenhuis

et al., 1998c) concerning ACEs to obtain more reliable results for comparison with previous studies.

77

Therefore, the significance of the results obtained from the ACE items in our study should be

considered as limited.

Biological studies have demonstrated the long-lasting consequences of childhood maltreatment

and neglect on the developing brain. They have shown that postnatal neglect or maltreatment

provokes a cascade of stress responses that organize the brain to develop along a specific pathway

selected to facilitate reproductive success and survival in a world of deprivation and strife. This

pathway, however, is costly because it is associated with an increased risk of developing serious

medical and psychiatric disorders and is unnecessary and maladaptive in a more benign

environment (Teicher et al., 2002).

6.6. The stability of dissociative symptoms

Dissociative symptoms were quite stable in our three-year follow-up study. The correlation

(r = 0.62) was on the same level as in a study with a student sample (n = 465) over two months

(r = 0.65) (Watson, 2003). The changes in DES-T scores followed a similar pattern to those of total

DES scores in all our study groups (Study IV). Dimensionally, the DES-T and the overall DES

scores therefore behaved similarly. The DES was originally developed to examine dissociation as a

continuum and was explicitly constructed to be a stable trait measure (Carlson and Putnam, 1993).

The stability of DES scores has been very good over shorter periods of time (Frischholz et al., 1990,

Van Ijzendoorn and Schuengel, 1996), but has not previously been studied over such a long follow-

up period or in the general population. In Study IV, characteristically different groups could be

detected. Stable high dissociators (2% of the whole sample and 29% of baseline high dissociators)

had the highest DES scores and considerable comorbidity, which is already discussed elsewhere.

The relationship between DES scores, BDI scores and suicidal ideation along with the

corresponding changes in the prevalence of diagnosed depression and suicidal ideation further

corroborates the comorbidity of dissociative symptomatology. However, it is not possible to

determine causality, for example whether depression actually gave rise to increased dissociation, or

whether the worsening dissociative symptoms made the subjects more depressive. The changes in

DES scores over the follow-up period were distinct in the new and recovered cases; the participants

either had significantly elevated DES scores or low scores, a result already previously reported

(Waller and Ross, 1997).

The vast majority of our study subjects had constantly very low dissociation scores, and a small

proportion of individuals suffered from persistent dissociative symptoms. The pathological

dissociative symptoms showed similar changes to those in the total DES scores, but the stability of

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the other factors of the DES should also be studied further. A proportion of individuals had

significantly changing scores over the follow-up period, indicating that these individuals had a

tendency to experience more transient, state-like dissociative symptoms.

6.7. A categorical or dimensional construct?

The stability of the dissociative taxon membership was low. Only four subjects met the criteria

for taxon membership suggested by Waller and Ross (1997) at baseline and on follow-up, and most

of the individuals who were classified as taxon members in one assessment were identified as

nonmembers in the other. Thus, dissociative taxon membership showed less stability than the

continuous variables of dissociation.

Waller and coworkers (1996) stated that there are fundamentally two categorically different

types of dissociation and two types of dissociators. On the basis of their taxometric analyses they

determined that markers of non-pathological dissociation such as absorption and imaginative

involvement measure a dimensional construct, whereas markers of pathological dissociation such as

indicators of amnesia for dissociative states, derealization, depersonalization, and identity alteration

measure a latent class or typological construct. This supports the original view of Janet that there

are two types of individuals: those who experience chronic dissociative states and those who do not.

The former would be members of a pathological dissociative taxon (Waller et al., 1996).

One of the currently most controversial issues in the study of dissociative phenomena is whether

dissociation is a dimensional or a categorical construct. However, recent studies testing the taxonic

model have found little support for the theory of dissociation as a categorical construct. Watson

(2003) concluded that the dissociative taxon scores were only modestly stable and were

substantially less stable than the continuous variables of dissociation among college students during

a two-month period. Our results were similar, although the follow-up time was considerably longer

in our study. Furthermore, in a sample of 276 students and 204 psychiatric inpatients, the ability of

taxon membership to detect dissociative disorders (DD) was investigated on the assumption that

patients suffering from DD should be taxon members (Modestin and Erni, 2004). No statistically

significant relationship was found between taxon membership and the clinical diagnosis of a

dissociative disorder. Taxon membership indicated a higher frequency of dissociative experiences

but could not be equated with the presence of a dissociative disorder (Modestin and Erni, 2004).

Taxon membership probabilities were also only modestly associated with a depersonalization

disorder diagnosis (Simeon et al., 2003). However, different results have also been obtained. Taxon

membership showed good discriminant validity with respect to dissociative disorder diagnosis and

79

reported childhood abuse among 100 traumatized female outpatients, and elevated absorption scores

were also found in subjects with emotional abuse (Allen et al., 2002).

The categorical approach has added to our understanding of dissociative phenomena and future

research will reveal the justification of this theory. Our results question its validity, and perhaps a

hybrid of the two conceptualizations may prove to be more accurate, while much of current research

is based on the premise that dissociation is a continuous variable across both clinical and non-

clinical groups.

6.8. Methodological considerations

6.8.1. Study population and design

The population sample was a random sample of the inhabitants of the province of Kuopio in the

central-eastern part of Finland. The age of the study subjects at baseline was limited to between 25

to 64 years, thus covering the entire period of adulthood except for the elderly. The sample size was

larger than in any previous general population studies on dissociation, and the age range was also

slightly different from other studies (Akyüz et al., 1999; Ross et al., 1990; Seedat et al., 2002).

The response rates in our study were satisfactory. In the cross-sectional studies the response rates

were 68% (Study I), 60% (Study II), and 73% (Study III). In the follow-up, 51% of the initial

sample and 75% of the baseline respondents returned the questionnaire (Study IV). In Studies I-III,

more women than men responded to the questionnaire, and among males the respondents were

slightly older than the non-respondents. In Study IV both the non-responding men and women were

younger than the respondents. There was no statistically significant difference in the mean DES

score at baseline between the non-responding and responding men on follow-up, but the mean DES

score of the non-responding women was statistically higher than that of the responding women. The

loss of younger men at baseline and on follow-up is a limitation in generalizing our results to the

general population because of the negative association between the DES scores and age (Akyüz et

al., 1999; Ross et al., 1990). The difference in the DES scores between the responding and non-

responding women on follow-up also possibly indicated that some women with a high DES score

dropped out of the study.

80

6.8.2. The Dissociative Experiences Scale and Somatoform Dissociation Questionnaire

In this study both the DES and the SDQ-20 were found to have satisfactory internal consistency

in all phases. Psychometric evaluation of the DES has been performed in several previous studies

(Carlson and Putnam, 1993; Dubester and Braun, 1995; Van Ijzendoorn and Schuengel, 1996). Its

reliability has been very good, with a mean alpha reliability from 16 studies of 0.93 (Van

Ijzendoorn and Schuengel, 1996). The reliability coefficients in our studies were at the same level,

and the correlation was satisfactory between the DES scores in both phases (r = 0.62), both

indicating good homogeneity of the DES in our study. The psychometric evaluation of the Finnish

version of the DES has also been examined (Lipsanen et al., 2003). The Finnish version of the DES

in our study was translated into English and back into Finnish, and has been published on the web

site of the Sidran Institute (Tanskanen, 1997).

The internal consistency and convergent validity of the SDQ-20 (Nijenhuis et al., 1996, 1999),

and its construct validity has been measured (Nijenhuis et al., 1998b). The reliability alpha

coefficients in our Studies II and III were at a slightly lower level than in some previous studies

(Nijenhuis et al., 1996, 1998b; ar et al., 2000), and in a recent study (Espirito Santo and Pio-

Abreu, 2007), although similar results to ours have also been reported (El-Hage et al., 2002; Waller

et al., 2000).

ar and coworkers (2000) detected a test-retest Pearson’s correlation over one month of r = 0.95,

but their study included only 35 subjects. Spearman’s correlation between the SDQ-20 scores in our

two studies was lower (r = 0.51). These results indicate satisfactory reliability of the SDQ-20. The

Finnish version of the SDQ-20 was translated from English into Finnish by Antti Tanskanen (M.D.,

Ph.D.), but no translation back into English was performed. The current English version of the

SDQ-20 is published in a book by Ellert Nijenhuis (2004) and in one of his articles (2000). It has

also included questions on whether the phenomena in the statements are related to a known physical

illness. However, that version of the SDQ-20 is used more in the clinical work with patients than in

research. The order in which the statements are presented has no impact on the results (Nijenhuis,

personal information, 2007).

The correlation (r = 0.60) between the DES and the SDQ-20 (Study III) showed that

psychological and somatoform dissociation are to some extent overlapping constructs, and have

common features. Other studies have reported higher correlations of r = 0.76 ( ar et al., 2000),

r = 0.85 (Nijenhuis et al., 1999) and a similar correlation of r = 0.64 (El-Hage et al., 2002), but a

lower correlation (r = 0.51) has also been detected (Waller et al., 2000). These earlier studies have

81

usually been carried out on small and/or selected samples, which could explain the differences in

the results.

The use of cut-off scores to determine significant levels of dissociative experiences or to

distinguish dissociative disorders from other diagnostic categories has been examined in many

studies, but no unambiguous cut-off scores have been found. With higher cut-off scores the

possibility of missing positive cases increases, although the inclusion of false negatives decreases.

As our aim was to examine dissociative symptoms in the general population, we chose average cut-

off scores to indicate high levels of dissociation on the grounds of the previous literature (Draijer

and Boon, 1993; Ross et al., 2002; ar et al., 2000; Steinberg et al., 1991; Waller at al., 2001;

Waller and Ross, 1997).

Both the DES and the SDQ-20 are self-report measures. There are certain limitations to these

methods, mostly concerning the ability of individuals to evaluate and understand the meaning of the

items and the frequency of their occurrence in daily life. The DES was explicitly developed to be a

trait measure of dissociation. However, some individuals have scored very differently in our follow-

up study, suggesting that individuals tend to give answers to the items on the basis of their

immediate past experiences.

6.8.3. Other measures

The reliability of the BDI (Cronbach’s alpha 0.89) and the TAS-20 (Cronbach’s alpha 0.86) has

previously been measured in this general population sample (Honkalampi et al., 2000, 2001).

Suicidal ideation was assessed with only one question from the BDI instead of a validated

questionnaire, and the results should therefore be considered with caution. Nevertheless, previous

studies have used the same method (Hintikka et al., 2001b) or a similar one (Gunnell et al., 2004) to

assess the presence of suicidal tendencies in general population samples.

Mental disorders diagnosed or treated by a physician were self-reported, and their accuracy was

not examined. However, it has been reported that there is usually no overestimation in this issue

(Aromaa et al., 1989). While all mental disorders were assessed in the original questionnaire, we

limited our Study IV to depression. Other comorbities may also affect the course of dissociative

symptoms, but they were not assessed in this study. The comorbidity of dissociative symptoms,

both psychological and somatoform, should be further examined.

82

7. Conclusions

7.1. Conclusions from the results

1) The prevalence of pathological dissociation in Finland was at the same level as in previous

studies in North America. There were no differences between genders in the prevalence of

pathological dissociation. Pathological dissociation was strongly associated with depressive

symptoms, suicidal ideation and alexithymia cross-sectionally.

2) Symptoms of somatoform dissociation were common in the general population, and high

somatoform dissociation was associated with male gender, an older age, a low level of education,

unemployment, a reduced working ability, and a poor financial situation. We found a graded,

positive relationship between an increasing number of adverse childhood experiences and high

somatoform dissociation. Factors associated with family pathology were also significant, providing

evidence of the complex issue of somatoform dissociation and adverse childhood experiences.

3) Those with both high psychological and high somatoform dissociation showed strong

comorbidity with depressive symptoms and suicidal ideation, and they were also disposed to

considerable adversities with their working ability, health and financial and social situation. The

correlation between DES and SDQ showed that psychological and somatoform dissociation are to

some extent overlapping constructs and have common features.

4) Only a small proportion of the general population suffered from constantly high levels of

dissociative symptoms. Among the stable high dissociators, significant comorbidity existed with

depressive symptoms and suicidal ideation. The stability of the dissociative taxon membership was

weaker than the stability of the continuous variables of dissociation.

7.2. Suggestions for future research

The stability of somatoform dissociation should be investigated and compared with the results

already obtained for the stability of psychological dissociation. Including trauma variables in the

study design would address the possible associations between both psychological and somatoform

dissociation and trauma in the general population. The factors associated with recovery from

83

dissociation in the general population require further research. The possible role of other comorbid

diagnostic categories in addition to depression should also be assessed.

The relationship between dissociation and alexithymia merits further study, taking into account

possible gender differences, the factor structure of alexithymia and possible associations with

somatoform dissociation.

7.3. Clinical implications

The comorbidity of dissociation with persistent depressive symptoms and chronic suicidal

ideation should be noted in clinical practice, especially among patients with a history of childhood

traumatization. Using self-report questionnaires (DES and SDQ-20) might be helpful in the

assessment of dissociative symptoms and disorders. A routine inquiry into dissociative symtoms of

the patient should be as important as the assessment of other psychiatric symptoms.

84

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Appendix I

Dissociative Experiences Scale (DES) Dissosiatiivisten kokemusten asteikko

Ohjeet:

Tässä kyselylomakkeessa on 28 kysymystä kokemuksista, joita Sinulla saattaa ilmetä arkielämässäsi. Me olemme kiinnostuneita siitä, onko Sinulla, ja jos on, kuinka usein näitä kokemuksia silloin, kun et ole alkoholin tai huumeiden vaikutuksen alaisena. Pyydämme Sinua ystävällisesti vastaamaan kysymyksiin siten, että mietit, missä määrin kysymyksessä kuvailtu kokemus sopii Sinuun, ja ympyröimään sitten sopivan numeron, joka ilmaisee, kuinka suuren osan ajasta Sinulla on näitä kokemuksia.

Esimerkki:

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

© 1986: Originally published in English by Carlson EB & Putnam FW. All rights reserved. © 1997: Suomentanut Antti Tanskanen, KYS, psykiatrian klinikka. Kaikki oikeudet pidätetään.

Varsinaiset kysymykset (1-28):

1. Jotkut ihmiset havahtuvat yhtäkkiä huomaamaan autoa (tai polkupyörää tms.) ajaessaan tai ollessaan jonkin ajoneuvon (auton, bussin, junan tms.) kyydissä, että he eivät muista mitään koko matkasta tai osasta matkaa.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

2. Jotkut ihmiset havahtuvat yhtäkkiä huomaamaan, että kuunnellessaan jonkun puhetta he eivät ole kuulleet ollenkaan, tai ovat kuulleet vain osittain, mitä toinen puhui.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

3. Jotkut ihmiset havahtuvat yhtäkkiä huomaamaan olevansa jossakin paikassa, mutta heillä ei ole aavistustakaan siitä, miten he sinne olivat tulleet.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina) 4. Jotkut ihmiset havahtuvat yhtäkkiä huomaamaan pukeutuneensa vaatteisiin, joita he eivät muista pukeneensa ylleen.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

5. Jotkut ihmiset saattavat löytää tavaroidensa joukosta uusia esineitä, joita he eivät muista ostaneensa.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

6. Jotkut ihmiset kohtaavat joskus vieraita ihmisiä, joita he eivät tunne ja jotka puhuttelevat heitä toisella nimellä tai väittävät tavanneensa heidät aiemmin.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

7. Jotkut ihmiset kokevat joskus, että he tuntevat ikään kuin seisovansa itsensä vieressä tai katselevansa omia tekemisiään ja he todella näkevät itsensä ikään kuin katselisivat jotakin toista ihmistä.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

8. Joillekin ihmisille käy joskus niin, että heitä moititaan, koska he eivät tunne eivätkä tervehdi omia ystäviään ja perheenjäseniään.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

9. Jotkut ihmiset kokevat, että he eivät muista lainkaan tärkeitä tapahtumia (esim. koulun päättäjäisiä, häitä) omasta elämästään.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

10. Jotkut ihmiset kokevat, että heitä syytetään valehtelusta, vaikka he omasta mielestään eivät ole valehdelleet.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

11. Jotkut ihmiset kokevat peiliin katsoessaan, että peilistä näkyvä kuva ei ole heidän oma kuvansa.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

12. Jotkut ihmiset kokevat, että ihmiset, esineet ja maailma heidän ympärillään eivät ole todellisia.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

13. Jotkut ihmiset kokevat, että heidän kehonsa ei tunnu omalta.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

14. Jotkut ihmiset muistavat joskus jonkin menneen tapahtuman niin elävästi, että tuntevat ikään kuin elävänsä sen uudelleen.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

15. Jotkut ihmiset eivät ole varmoja siitä, ovatko tietyt asiat todella tapahtuneet niin kuin he muistelevat vai onko kaikki ollut vain haaveilua tai unta.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

16. Jotkut ihmiset kokevat tutussa paikassa ollessaan, että tuo tuttu paikka on outo ja vieras.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

17. Jotkut ihmiset eläytyvät ja tempautuvat mukaan katsomaansa TV-ohjelmaan tai elokuvaan niin täysin, etteivät he ole tietoisia ympäristön tapahtumista.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

18. Jotkut ihmiset huomaavat uppoavansa niin syvälle kuvitelmiinsa tai haaveisiinsa, että heistä tuntuu siltä, kuin nuo asiat todellisuudessa tapahtuisivat heille.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

19. Jotkut ihmiset huomaavat pystyvänsä joskus olemaan kiinnittämättä huomiota kipuun.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

20. Jotkut ihmiset löytävät itsensä joskus tuijottamasta tyhjyyteen, niin että he eivät ajattele mitään eivätkä huomaa ajan kulumista.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

21. Jotkut ihmiset huomaavat joskus yksin ollessaan puhuvansa ääneen itselleen.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

22. Jotkut ihmiset kokevat, että he saattavat toimia hyvin eri tavalla jossakin tilanteessa kuin jossakin toisessa tilanteessa. Heistä tuntuu, ikään kuin he olisivat noissa eri tilanteissa kaksi eri ihmistä.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

23. Jotkut ihmiset kokevat joskus, että he tietyissä tilanteissa (esim. urheilussa, työssä, juhlissa, asioimistilanteissa, muiden kanssa keskustellessaan tai seurustellessaan, jne.) pystyvät tekemään tiettyjä asioita hämmästyttävän helposti ja vaistomaisesti, vaikka ne tavallisesti olisivat heille vaikeita.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

24. Jotkut ihmiset kokevat joskus, että he eivät voi muistaa, ovatko he todella tehneet jonkin asian vai ovatko he vain ajatelleet tehneensä sen (esim. eivät muista, ovatko postittaneet kirjeen tai vain ajatelleet postittaneensa sen).

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

25. Jotkut ihmiset löytävät todisteita siitä, että he ovat tehneet jotakin, mitä he eivät muista tehneensä.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

26. Jotkut ihmiset löytävät joskus tavaroidensa joukosta kirjoituksia, piirustuksia tai muistiinpanoja, jotka heidän on täytynyt tehdä mutta joita he eivät voi muistaa tehneensä.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

27. Jotkut ihmiset huomaavat joskus kuulevansa päänsä sisältä ääniä, jotka kehottavat heitä tekemään jotain tai ottavat kantaa siihen, mitä he tekevät.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

28. Joistakin ihmisistä tuntuu joskus siltä, että he ikään kuin katselevat maailmaa sumuverhon läpi, niin että ihmiset ja esineet näyttävät olevan kaukana tai epäselviä.

Ympyröi se prosenttiluku, joka parhaiten ilmaisee sen, kuinka usein tällaista Sinulle tapahtuu.

0 % 10 20 30 40 50 60 70 80 90 100 % (ei koskaan) (aina)

Appendix II

Somatoform Dissociation Questionnaire (SDQ-20) Somatoformisen dissosiaation mittari

Seuraava kysymyssarja käsittelee kokemuksia, joita joillakin ihmisillä voi olla joskus. Ympyröikää jokaisen kysymyksen kohdalla jokin numeroista 1-5.

1 = ei sovi minulle lainkaan 2 = saattaa sopia minulle 3 = sopii minulle 4 = sopii minulle hyvin 5 = sopii minulle erinomaisesti

ei sovi minulle sopii minulle sopii minulle lainkaan erinomaisesti

1. On niin, että ikään kuin kehoni, tai osa siitä, olisi kadonnut. 1 2 3 4 5

2. Olen halvaantunut jonkin aikaa. 1 2 3 4 5 3. En voi puhua (tai vain suurin ponnistuksin),

tai voin vain kuiskata. 1 2 3 4 5 4. Kehoni, tai osa siitä, on tunnoton kivulle. 1 2 3 4 5 5. Tunnen virtsatessa kipua. 1 2 3 4 5 6. Jonkin aikaa on niin, etten voi nähdä (ikään

kuin olisin sokea) 1 2 3 4 5 7. Minulla on virtsaamisvaikeuksia. 1 2 3 4 5 8. Jonkin aikaa on niin, etten voi kuulla (ikään

kuin olisin kuuro) 1 2 3 4 5 9. Kuulen läheltä tulevat äänet niin, ikään kuin

ne tulisivat kaukaa. 1 2 3 4 5 10. Jäykistyn hetkeksi. 1 2 3 4 5 11. Minulla ei ole flunssaa, mutta silti pystyn

haistamaan paljon paremmin tai huonommin kuin tavallisesti. 1 2 3 4 5

12. Tunnen kipua sukupuolielimissäni (muulloin kuin yhdynnässä). 1 2 3 4 5

13. Minulla on kohtaus, joka muistuttaa epileptistä kohtausta. 1 2 3 4 5

14. Tunnen vastenmielisyyttä tuoksuihin, joista yleensä pidän. 1 2 3 4 5

15. Tunnen vastenmielisyyttä makuihin, joista yleensä pidän (naisilla muulloin kuinraskauden ja kuukautisten aikana). 1 2 3 4 5

16. Näen esineet ympärilläni eri tavalla kuin yleensä (esim. ikään kuin katselisin tunnelin läpi tai näkisin vain osan kohteesta). 1 2 3 4 5

17. En voi nukkua öitäni loppuun saakka, mutta pysyn hyvin aktiivisena päiväsaikaan. 1 2 3 4 5

18. En voi niellä, tai vain suurin ponnistuksin. 1 2 3 4 5 19. Ihmiset ja esineet näyttävät suuremmilta

kuin ne todellisuudessa ovat. 20. Kehoni, tai osa siitä, tuntuu puutuneelta. 1 2 3 4 5

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