476Joumal of Intellectual Disability Research

VOLUME 41 PART 6 pp 476-480 DECEMBER I997

Manifestations of depression in people with intellectual

disability

G. M. Marston, D. W. Perry & A. Roy

Brooklands, Birmingham, England

Abstract

The symptoms of 36 people with varying degrees of

intellectual disability (ID) who had had an ICD-IO

depressive syndrome in the preceding year were

compared with 46 non-depressed people with

comparable degrees of ID. Throughout the spectrum of

ID, symptoms of depressed affect and sleep disturbance

were significantly different between the groups. While

symptoms in people with mild ID were reflected in the

standard diagnostic criteria, this was not the case in

people with moderate and severe ID. With increasing

disability there was a move towards 'behavioural

depressive equivalents' such as aggression, screaming and

self-injurious behaviour. Diagnostic criteria for

depression among people with severe ID, should place

more emphasis on behavioural 'depressive equivalents'.

Keywords depression, behavioural equivalents, newdiagnostic criteria

Introduction

In the last few years, there has been an increasingnational interest in depression, highlighted by the1992 Defeat Depression Campaign (RCGP & RCP1992). In 1995, the Health of the Nation document

Correspondence: Dr Ashok Roy, Consultant Psychiatrist,Brookiands, Coleshill Road, Marston Green, Birmingham B377HL, England.

for people with intellectual disability (Department ofHealth 1995) issued a challenge to reduce ill healthand death caused by mental illness, includingdepression. However, depression must be recognizedfirst before people suffering from it can be treated.Paykel & Priest (1992) stated that up to soVo ofdepressive illnesses in the general population are notproperly recognized at the first interview with aprimary care doctor.

In the population with intellectual disability (ID),it is more likely that mental illness goes unnoticedfor a number of reasons. There can be a tendency toattribute abnormal behaviours to people with ID,which leads to 'diagnostic overshadowing' (Reiss etal. 1982). Symptoms may be non-disruptive, whichlessens the likelihood that these clinical signs will beregarded as problems by carers. Depressive disordermay be difficult to diagnose because of impairedcommunication and the modifying effects ofunderlying brain damage (Yappa & Roy 1990).

In recent years, researchers have tried to delineatesymptoms of depressive illness viithin the populationwith ID (Bregman 1991). Much of this work hasconsisted of single case reports or has been focusedon specific sub-populations, such as those withpervasive developmental disorder (Ghaziuddin &Tsai 1991) or Down's syndrome (Cooper &Collacott 1994). When more general populationshave been studied, the focus has been on severedepression and associated symptomatology (Meins

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G. M. Marston et al • Manifestations of depression

1995). If symptoms of depression are markedlydifferent in the population with ID, such strictcriteria would inevitably exclude potential cases andlead to unrepresentative data. There would also beassociated validity problems in groups with severe/profound ID. Many different methodologies havebeen employed by researchers, which has preventeda meaningful comparison of results.

In an attempt to avoid under-diagnosis, thepresent study compared symptoms in a broadlydiagnosed depressive group (ICD-io) with a non-depressed group of people with ID. By identifyingwhich symptoms and signs were seen significantlymore frequently in the depressed group at each levelof ID, it was hoped to demonstrate the significanceof atypical 'behavioural depressive equivalents' withan increasing degree of ID.

Materials and methods

Identification of client group

The study was conducted in the West Midlands,England, in an area with a population of 158 000.Eighty-two clients with ID were identified over a 3-month period from those registered with the local IDservice and under the care of the local consultantpsychiatrist. These included hospital in-patients,community-based clients in both NHS and privatesector hostels, and clients living at home.

Administration of the checklist

For each subject, a standard checklist (see'Appendix i'), which comprised of 30 symptomsderived from the ICD-io diagnostic criteria (WHO1992) and the Disability Assessment Schedule(Holmes et al. 1982), was completed with the clientand a carer who had known the person for over ayear (by GM). This checklist looked for changes inbehaviour or symptoms (either new or exacerbationsof existing traits) which had lasted for at least 2weeks and occurred within the previous 12-months.The diagnosis was done blind and enquiries weremade about as many as possible of the 30 symptoms.It was not easy to assess in people with severe andprofound ID; for example, assessment of depressedmood in some of this group was based on anamalgamation of the carers' subjective feelings, and

observations and/or interpretations made by therater. An assessment of the level of ID was made,using a checklist derived from ICD-io criteria, basedon skills attained and level of functioning in variousdomains.

Clinical diagnosis of depression

A second independent assessor (DP) thenscrutinized the patients' medical records. If an ICD-io diagnosis could be made at the time when theabnormal symptoms were present, then no furtheraction was taken and the diagnosis was recorded.However, if no diagnosis was made at the time whenthe abnormal symptoms were present or therecorded data to confirm the diagnosis wasinsufficient, then the second assessor conductedrepeat interviews with client and/or carer to make adiagnosis blind to the first assessor. This led to theformation of two groups, the first having a diagnosisof a depressive disorder according to ICD-10criteria, and the second with either an alternativediagnosis or no psychiatric disorder.

Symptom analysis

The prevalence of symptoms was ascertained in thetwo groups (depressed versus non-depressed/otherdiagnosis). Variations in symptom presentation werethen analysed using chi-squared tests with Yate'scorrection to assess any difference between thedeferring levels of ID (mild, moderate and severe/profound) in the two groups.

Results

Out of the 82 patients interviewed with their carersby the first assessor (GM), 36 were thought to have adepressive disorder, classified in ICD-io criteria(Table 1), by the second assessor (DP). Ten subjectsfell into the category of severe depressive episode,one with psychotic features. Eleven patients haddepressed episodes of a moderate to mild degree.Five subjects had either a bipolar disorder orrecurrent depressive episodes. The remaining 10patients had less definable disorders, most beingeither 'unspecified' or 'other'.

Within the depressed group, one person was

1997 Blackwell Science Ltd, Joumal of Intellectual Disability Research 41, 476-480

478Journal of Intellectual Disability Research VOLUME 41 PART 6 DECEMBER 1997

G. M. Marston et al • Manifestations of depression

Table I Categories of the depressive syndromes diagnosed (ICD-IO)

Table 2 Frequency with which symptoms were present in the de-

pressed and non-depressed groups

Depresssive syndrome Nutnber

Severe depressive episode vi/ithpsychotic symptoms I

Severe depressive episode 9Moderate depressive episode 8Mild depressive episode 3Other depressive episode 3Unspecified mood disorders SRecurrent depressive disorder and bipolar disorder 5Dysthmia IAdjustment reaction depressed type ITotal 36

receiving medication for epilepsy and one was takingPropranolol. One patient had carcinoma of thebreast (in remission) and another had adequatelytreated hypothyroidism. In the non-depressed group,three subjects were receiving medication for epilepsyand one had adequately treated congenitalhypothyroidism.

The mean age ofthe depressed group was 28years (range 15-58 years); there were 10 males and26 females. Seventeen patients had mild ID, 11 hadmoderate ID and eight had profound/severe ID.Two people with a pervasive developmental disorderand two with Down's syndrome were included in thesample. Table 2 shows the frequency with which aparticular symptom from the check list occurred inthe depressed versus non-depressed/other diagnosisgroups.

By stratifying the two groups into different levelsof ID (i.e. mild, moderate and severe/profound),comparison by chi-squared testing could be made tosee which symptoms from the checklist weresignificantly different (P < 0.05) between the twogroups (Table 3).

It can be seen that core symptoms of sleepdisturbance and depressed mood were notedsignificantly more frequently in the depressed groupacross all levels of ID. In the mild ID group, othersignificantly different symptoms were diurnal moodvariation, loss of energy, loss of interest and weightloss. These symptoms were closely allied to thoseseen in standard diagnostic criteria. Loss ofconfidence and tearfulness were also seen

Symptom

Depressed affectTearfulnessLoss of interestLack of emotional

responseSleep disturbanceDiurnal variation

of moodPsychomotor

agitationPsychomotor

retardation

Loss of appetiteWeight lossLoss of libidoLoss of confidence

Unreasonableself-reproach

Suicidal ideationSelf-injurious

behaviourPoor

concentrationDelusion (mood

congruents)Loss of energyConstipationAnxietyObsessional/

compulsivebehaviour

AggressionIrritabilityLabile moodReduced

communicationSocial isolationRunning awayScreaming

Anti-socialbehaviour

Stereotypedbehaviour

Depressed (%)

88SO66

2783

27

33

162227II16

2216

SO

22

3282228

17

332817

28

3317

28

28

17

Other diagnosis

no mental illness (%)

13138

1717

4

22

913749

44

14

7

079

13

22222213

999

II

9

13

significantly more frequently. In the moderate IDgroup, the pattern changed, except for weight loss,with self-injurious behaviour, reducedcommunication and social isolation becomingsignificantly different. This trend towards

© 1997 Blackwell Science lAd, Joumal of Intellectual Disability Research 41, 476-480

479

Journal of Intellectual Disability Research VOLUME 41 PART 6 DECEMBER I997

G. M. Marston et al • Manifestations of depression

Table 3 Symptoms present with a level of significance of P < 0.05in depressed versus non-depressed groups of subjects with thesame degree of intellectual disability

Level of intellectual disability Symptom

Mild

Moderate

Severe/profound

Depressed affectSleep disturbanceTearfulnessDiurnal mood variationLoss of energyLoss of interestLoss of confidenceWeight loss

Depressed affectSleep disturbanceSocial isolationSelf-injurious behaviourReduced communicationWeight loss

Depressed affectSleep disturbanceScreamingAggressionSelf-injurious behaviourReduced communication

'behavioural depressive equivalents' continued in thesevere/profound ID group, with the significance ofweight loss and isolation being replaced byscreaming and aggression.

Discussion

Previous studies have recognized that standarddiagnostic criteria, such as DSM-III-R, caneffectively be used to detect depression associatedwith mild ID (Meins 1995) and that a spectrum ofsymptoms may be linked to depression (e.g.aggression, screaming and self-injurious behaviour).It has also been stated that these standard criteriabecome less useful when applied to the moreseverely disabled people with limited language.

The present study supports these views. In themildly disabled group, all three core features of theICD-IO depressive category (i.e. depressed mood,reduced energy and reduced interest) were foundwith significantly higher frequency in the depressedgroup compared to the non-depressed group. With

increasing disability, only depressed mood and sleepdisturbance retained their significance. At theselevels 'behavioural depressive equivalents' were morefrequently displayed (e.g. screaming, self-injuriousbehaviour and aggression). It is likely that thesechanges reflect the impact of developmental levels(Chariot et al. 1993) in the same way that depressionpresents differently in children to adults. Unlikeother studies, the present authors were surprised tofind that irritability was not as significant asdepressed mood (particularly in the severe/profoundID group).

The present study had some of the methodologicalproblems mentioned in the introduction, including arelatively small sample size in the profound/severeID range. The groups were not matched for age orsex. Some subjects were treated for epilepsy, whichmight have contributed to depressive features(Robertson 1989). Some symptoms were hard toelicit from the more disabled patients, so the authorshad to rely on the reports of carers. However, byrepresenting a wide range of depressive categories,an attempt was made to avoid under-diagnosis,although over-inclusion might occur in the vaguercategories such as 'other' and 'unspecified'.

Despite these problems, the present results addweight to the argument that researchers should moveaway from criteria used in the general populationand incorporate more behavioural depressiveequivalents into criteria for people with ID. Cooper& CoUacott (1996) put forward theKetteringLeicester diagnostic criteria, which havegood face validity, and suggested that these shouldbe used widely and adapted in the light ofexperience. Meins (1996) has also suggested using asub-scale of the Comprehensive PsychopathologicalRating Scale, the MRDS, which differentiates majordepression from other depressive disorders.

To support the diagnosis of depression based onsuch scales, other factors could be considered, suchas family history, past depressive episodes and lifeevents. Further evidence could be gleaned fromresponses to therapeutic interventions(pharmacological and psychological).

It would seem that any meaningful step forward inthe reliable assessment of depression in thepopulation with severe ID will only be taken bycombining all these approaches in a larger-scale,collaborative, pt'ospective research project.

1997 Blackwell Science Ltd, Journal of Intellectual Disability Research 41, 476-480

480Joumal of Intellectual Disability Research VOLUME 41 PART 6 DECEMBER 1997

G. M. Marston et al • Manifestations of depression

Acknowledgement

The authors would like to thank all the secretarialstaff of Brooklands for their tolerance and help intyping this paper.

References

Bregman J. D. (1991) Current developments in theunderstanding of mental retardation: Part II.Psychopathology. Joumal ofthe American Academy ofChild and Adolescent Psychiatry 30, 861-72.

Chariot L. R., Doucene A. C. & Mezzacappa E. (1993)Affective symptoms of institutionalised adults withmental retardation. American Joumal on MentalRetardation 98, 408-16.

Cooper S. A. & Collacott R. A. (1994) Clinical featuresand diagnostic criteria of depression in Down'ssyndrome. British Joumal of Psychiatry 165, 399-403.

Cooper S. A. & Collacott R. A. (1996) Depressive episodesin adults with learning disability. Irish Joumal ofPsychological Medicine 13, 105-13.

Department of Health (1995) The Health ofthe Nation: AStrategy for People with Leaming Disabilities. HMSO,London.

Ghaziuddin M. & Tsai L. (1991) Depression in autisticdisorder. British Joumal of Psychiatry 159, 721-3.

Holmes N., Shan A. & Wing L. (1982) The DisabilityAssessment Schedule: a brief screening device for usewith the mentally retarded. Psychological Medicine I2,879-90.

Meins W. (1995) Symptoms of major depression inmentally retarded adults. Joumal of Intellectual DisabilityResearch 39, 41-5.

Meins W. (1996) A new depression scale designed for usewith adults with mental retardation. Joumal of IntellectualDisability Research 40, 222-6.

Paykel E. S. & Priest R. G. (1992) Depression in generalpractice: consensus statement. British Medical Joumal305,1198-202.

Reiss S., Levitan G. W. & Szysizko J. (1982) Emotionaldisturbance and mental retardation: diagnosticovershadowing. American Joumal of Mental Deficiency 86,567-74-

Robertson M. M. (1989) The organic contribution todepressive illness in patients with epilepsy. Joumal ofEpilepsy 2, 189-230.

Royal College of Psychiatrists and Royal College of GeneralPractitioners (1992) Defeat Depression Campaign. RoyalCollege of Psychiatrists and Royal College of GeneralPractitioners, London.

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Received ij January 7997

Appendix I

Features of depressive episodes in people withintellectual disability

Patient's name: DOB: ...

Address/ward: Sex:

Informant: Recurrent/single: ...

Clinical feature lasting 2 weeks or more

Depressed affectTearfulnessLoss of interestLack of emotional responseSleep disturbance (state type)Diurnal variation of moodPsychomotor agitationPsychomotor retardationLoss of appetiteWeight loss (5% body mass in one month)Loss of libidoLoss of confidenceUnreasonable self-reproachSuicidal ideationSelf-injurious behaviourDelusion (mood congruents)Loss of energyConstipationAnxietyObsessional/compulsive behaviourAggressionIrritabilityLabile moodReduced communicationSocial isolationRunning awayScreamingAnti-social behaviourStereotyped behaviourPoor concentration

Degree of intellectual disability (lCD-10)

MildModerateSevere/profound

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© 1997 Blackwell Science Ltd, Joumal of Intellectual Disability Research 41, 476-480