A prospective analysis of life events, problem behaviours and depression in adults with intellectual disability

Journal of Intellectual Disability Research doi: 10.1111/j.1365-2788.2005.00816.x

pp

–

248

The Authors, Journal Compilation ©

Blackwell Publishing Ltd

Blackwell Publishing LtdOxford, UKJIRJournal of Intellectual Disability Research0964-2633© 2005 The Authors, Journal of Intellectual Disability Research (2005)50

4248258

Original Article

Life eventsA. J. Esbensen & B. A. Benson

Correspondence: Anna Esbensen, Waisman Center, University of Wisconsin-Madison 1500 Highland Avenue, Madison, WI 53705, USA (e-mail: [email protected]).

A prospective analysis of life events, problem behaviours and depression in adults with intellectual disability

A. J. Esbensen & B. A. Benson

Ohio State University, Columbus, OH, USA

Abstract

Background

Life events have consistently been found to be associated with behaviour problems and depression among individuals with intellectual dis-ability (ID). However, prior findings have typically been based on correlational or retrospective analyses of case files. The current study attempted to replicate prior findings from life events with concurrent data and extend them to the prospective prediction of behaviour problems and depression. The influence of impact ratings of life events was also explored.

Methods

Seventy-four informants rated

adults with ID on measures of life events, behaviour prob-lems and depressive symptoms. Life events were rated as having either a positive, negative or no impact on the life of the individual with ID. Measures were completed twice, at a

-month interval.

Results

Behaviour problems were both correlated with and predicted by frequency counts of life events and life events perceived as negative. However, the predictive ability depended on which measure of problem behaviour was selected. Positive life events were not associated with concurrent behaviour prob-lems. Depressive symptoms were correlated with all life changes, but only predicted by frequency counts

of life events and life events perceived as negative. Again, the predictive ability depended on which mea-sure of depression was selected. Findings were cor-roborated with a group of individuals with clinical diagnoses of major depression.

Conclusions

Frequency counts of all life events and life events perceived as negative play a role in the development of behaviour problems and depressive symptoms among adults with ID. The results have implications for interventions for behaviour problems following a life event, and for reducing depressive symptoms for adults with mild ID.

Keywords

behaviour problems, depression, intellectual disability, life events

Introduction

A life event has been defined as an experience or event with an established origin and short duration, which can be related to a person’s psychological con-dition (Goodyer

). Stressors and life events are an important area of study in the lives of individuals with intellectual disability (ID) as they have potential implications for triggering depression, psychopathol-ogy and problem behaviours. Preliminary works in this field have typically supported a positive associa-tion between life events and psychopathology or behaviour problems (Hastings

et al

.

; Hatton &

Journal of Intellectual Disability Research

A. J. Esbensen & B. A. Benson •

Life events249



Emerson

; Owen

et al

.

). However, all stud-ies to date have been correlational or based on retro-spective analyses of case files. Prospective studies are needed to determine the causal effect of life events on behaviour problems and depression.

Early work on life events among individuals with ID searched for differences in the frequency or nature of life events compared with the general population. Stack

et al

. (

) examined differences between a sample of individuals with ID and one from the gen-eral population on the type and number of life events experienced in the month prior to admission to a mental health hospital. It was found that individuals with ID experienced on average fewer life events compared with the control sample. It was also found that

% of the life events experienced by individuals with ID involved interpersonal conflict compared with only

% among the controls. The authors con-cluded that among intakes to a mental health facility, the type of stressful event was more important than the number of events in precipitating admission.

The literature on life events among individuals with ID has since primarily focused on the associa-tion between stressful life events and behaviour prob-lems. In an examination of referrals for treatment of behaviour disorder, Ghaziuddin (

) found that individuals with ID who experienced a stressful life event were higher functioning than those who did not experience any stressful life event. He concluded that life events had a significant impact on referrals for behaviour problems among individuals with ID, and that this was particularly the case for individuals functioning in the mild range of ID. Monaghan & Soni (

) examined significant life events from the past

months and their association with social func-tioning and behaviour disorders among adults with ID. No differences were found in the type of life events experienced by individuals experiencing high or low frequency of life events, but differences were found on measures of behaviour problems and self-care, with individuals experiencing fewer life events performing better. The finding was substantiated by significant correlations between the frequency of life events and changes in behaviour problems or self-care over

months of assessment. A significant asso-ciation between life events and behaviour problems has also been supported among children with Down syndrome (Coe

et al

.

). This study found that the children with Down syndrome experienced fewer life

events in the preceding

months, comparable fre-quency of negative life events and more behaviour problems than typically developing children. Most recently, life events from the preceding

months have been tied to elevated reports of aggressive behaviour (Owen

et al

.

). These ratings of the life events of adults with developmental disabilities in long-term residential settings were significantly cor-related with aggressive/destructive behaviour as mea-sured by the Behavior Problem Inventory, but not with self-injurious or stereotyped behaviour. These studies lend support to the association between life events and the presence of behaviour problems.

While the literature has primarily focused on life events in relation to behaviour problems, researchers have begun to focus on the relationship between life events and psychopathology. Among children with ID, those who experienced two or more life events were at a higher risk of having conduct or emotional disorders as assessed by the Development and Well Being Assessment (Hatton & Emerson

). Among adults with ID, experiencing one or more life events in the last year significantly increased the odds ratio predicting affective disorders as measured by the Psychiatric Assessment Schedules for Adults with Developmental Disabilities (PAS-ADD), but not psy-chotic or organic disorders (Hastings

et al

.

). Also, individuals meeting criteria on the PAS-ADD for affective/neurotic disorders experienced signifi-cantly more life events compared with controls (Owen

et al

.

). No differences were found between individuals meeting criteria for psychotic disorders and controls. These findings indicate that life events may play a role in the development of affective/neurotic disorders.

In a study focusing specifically on the relationship between life events and depression, Cooper & Colla-cott (

) determined that adults with Down syn-drome experiencing recurrent depression were less likely to have significant life events recorded in clinic notes prior to a recurrence compared with cases of a single episode of depression. The finding indicates that the association between depression and life events may be influenced by the duration and recur-rence of the psychiatric illness, with life events play-ing a smaller role in predicting depression over time. This leads us to question whether other events not identified in the clinic notes may have played a role in the recurrence of depression.



Life events250



A common limitation of these prior studies is that causal inferences cannot be drawn from retrospective or cross-sectional designs regarding the relationship between life events and behaviour problems or depression. There is a need for prospective studies to establish the causal impact of life events on individ-uals with ID (Hatton & Emerson

; Owen

et al

.

). Another limitation is that all life changes are considered by researchers to be negative or stressful. However, the impact of a life event depends on the perspective of the person who experiences it. For example, changes in the frequency of visits to or from family have been considered to be a negative event. Yet, the increase in contact could be viewed as a positive change. Likewise, moving to another location at work or in a residential setting could be viewed as a positive event if done to avoid a disturbing or upset-ting situation. As Stack

et al

. (

) found that the nature of the event was more important than the frequency of events; life events need to be evaluated by the rater as to whether they had a positive or negative impact on the individual being rated, rather than the researcher assuming that all changes are negative. Also, drawing on the questions raised from the study by Cooper & Collacott (

), it is worth examining the impact of all life events, not only those considered significant by the investigators.

The current study sought to avoid these common limitations of not being able to make causal infer-ences between life events and depression or behav-iour problems, and of considering all events as negative. First, the current study sought to confirm the concurrent relationship between life events, behaviour problems and depressive symptomatology. Based on the findings of Owen

et al

. (

) and Hastings

et al

. (

), it was hypothesized that an increase in the frequency of life events would be associated with an increase in concurrent behaviour problems and an increase in reports of depressive symptoms. Further, it was hypothesized that these relationships would hold and be stronger when assessed with life events viewed as negative specific to the individual being rated, and would be the inverse or non-significant when assessed with life events viewed as positive. Second, the current study examined the causal association between life events and subsequent depressive symptomatology and behaviour problems using a prospective design. It was hypothesized that, when controlling for earlier

reports of depressive symptoms or behaviour prob-lems, experiencing more life events would signifi-cantly predict future behaviour problems and depressive symptoms. Further, it was hypothesized that this relationship would hold for events viewed as negative and not for events viewed as positive.

Methods

Informants and individuals rated

Seventy-four informants rated

adults with ID that they knew well and for longer than

months as part of a larger study on the development of depres-sion (Esbensen & Benson

). Informants were primarily female (

%), Caucasian (

%), and had more than

years of experience in the field (

%). They ranged in age from

to

years (M

=

.

, SD

=

.

). Informants provided data on a maximum of three adults. Individuals rated had a diagnosis of borderline intellectual functioning (

%), mild (

%), moderate (

%) or severe (

%) ID based on agency records, and the level of intellectual functioning was not disclosed for

% of individuals rated. Individuals were primarily male (

%), Caucasian (

%), in competitive (

%), supported (

%) or sheltered employment (

%) and living in the community with supports (

%). They ranged in age from

to

years (M

=

.

, SD

=

.

). The following Diag-nostic and Statistical Manual of Mental Disorders – Fourth Edition (DSM-IV) psychiatric diagnoses were obtained from the individuals’ current psychiatric records: major depression,

; bipolar disorder,

; dysthymia,

; mood disorder,

; other,

; and

reported no psychiatric diagnoses.

Measures

Life events

The Life Experiences Survey (LES, Sarason

et al

.

) is a

-item questionnaire, measuring life changes during the last

months, and/or

year. This instrument allows the subject to indicate the presence or absence of an event, and then to rate the impact of the event. Informants indicated the extent to which the individuals being rated viewed the event as having a positive, negative or no impact on their life at the time the event occurred. The instrument was



Life events251



modified to examine life experiences over the last

months. In addition, three items were removed as they rarely apply to the subject population. These included foreclosure on a mortgage or loan, borrow-ing more than $

, and borrowing less than $

. This resulted in a

-item scale. An open-ended question is included to identify other life expe-riences not included in the LES that occurred in the previous

months.

Behaviour problems

The Aberrant Behavior Checklist (ABC) contains

items assessing behaviour problems among individu-als with ID and developmental disabilities (Aman

et al. a). The items factor onto five subscales: () irritability, agitation, crying; () lethargy, withdrawal; () stereotypic behaviour; () hyperactivity/non-compliance, and () inappropriate speech. Items are rated on a -point Likert-type scale, assessing the degree to which each behaviour item is a problem. Internal consistency is generally high; retest reliability and inter-rater reliability are generally found to be acceptable (Aman et al. a,b; Aman ; Rojahn & Helsel ). The validity of the ABC has been extensively supported.

The Problem Behavior Scale on the Scales of Inde-pendent Behavior – Revised (SIB-R) contains eight items measuring maladaptive behaviours (Bruininks et al. ). Administered in either a structured inter-view format or a checklist, this instrument is appro-priate for individuals aged birth to over . The maladaptive behaviour portion of the instrument contains three subscales: internalized maladaptive index (hurtful to self, unusual or repetitive habits, and withdrawn or inattentive behaviour), asocial mal-adaptive index (socially offensive behaviour and uncooperative behaviour) and externalized maladap-tive index (hurtful to others, destructive to property and disruptive behaviour). If an individual problem behaviour is present, then frequency and severity scores are obtained. Index scores can be calculated for individual items, for subscales and for the total scale. The index scores provide ratings of the serious-ness of the problem behaviour as normal, marginally serious, moderately serious, serious or very serious. Scoring has been reversed in the current study so that a high score represents a more serious behaviour problem. Reliability and validity are excellent for the Problem Behavior Scales (Bruininks et al. ).

Depression

The Anxiety, Depression and Mood Scale (ADAMS) is a -item informant-report instrument designed to screen for symptoms of affective disorders (Esbensen et al. ). The scale factors onto five subscales of depressed mood, manic/hyperactive behaviour, social avoidance, general anxiety and compulsive behav-iours. The ADAMS has sound psychometric reliabil-ity for the total scale and subscales, and good validity with psychiatric diagnoses for the subscales. The ADAMS has yet to be tested for convergent validity with other instruments.

The Assessment of Dual Diagnosis (ADD) was developed as a screening instrument based on DSM-IV criteria (Matson & Bamburg ). It is a successor to the more commonly known PIMRA (Psychopathology Instrument for Mentally Retarded Adults). An informant-report measure with fre-quency, duration and severity measures, the ADD contains items on subscales corresponding to particular disorders in DSM-IV. Only the frequency measure of the depression subscale was used in the current study. Internal consistency for the entire ADD scale is reported to be high. Inter-rater reliabil-ity is also high as is test–retest reliability. Little pub-lished material is available for this instrument that is intended to screen for psychopathology among indi-viduals with mild and moderate ID; however, the ADD appears to be a promising instrument for the measurement of psychopathology.

Procedures

Informants were recommended by agencies provid-ing services to individuals with ID. All agencies pro-vided services to individuals with ID who were receiving assistance with adaptive life skills on a daily or weekly basis. Adults were living in houses and apartments with fewer than five roommates. Consent was obtained from the adults with ID or their legal guardian, and from the informant. The informant completed a battery of instruments at Time , and again after approximately a -month interval at Time . Informants were entered into $ lotteries upon completion of the instruments. A -month interval between ratings was used to accommodate the con-straints of a larger study on the development of depression (Esbensen & Benson ).


A. J. Esbensen & B. A. Benson • Life events252

The Authors, Journal Compilation © Blackwell Publishing Ltd

Data analysis

Bivariate correlations were used to investigate the first hypothesis, how Time measures of behaviour prob-lems and depressed mood were associated with three different concurrent measures of life events. Life events were measured using a total frequency count of all life events in the past months as measured at Time , and then again as a frequency count of the life events perceived as having either a negative or a positive impact on the individual with ID at Time . T-tests were used to further explore the first hypoth-esis. Individuals with a clinical diagnosis of major depression were compared with the rest of the sample on measures of all life events, life events perceived as negative and life events perceived as positive.

Multiple hierarchical regression was used to inves-tigate the second hypothesis, how life events over the last months predicted changes in depressed mood and behaviour problems. Analyses were conducted separately for the subscales or measures of behav-iour problems and the two measures of depressed mood, all measured at Time . In all analyses, iden-tified covariates and the Time measures of the dependent variables were entered into the regression model. Next, Time life events were entered into the model to predict the dependent variable. By control-ling for Time measures of the dependent variables, we are able to determine causal effects of life events on the dependent variables at Time (Cohen et al. ). Multiple hierarchical regression was also used to investigate the hypothesis that life events perceived as negative would have a greater influence than life events perceived as positive on subsequent behaviour problems or depressed mood. After controlling for covariates and the Time measures of the dependent variables, measures of life events perceived as nega-tive at Time was entered simultaneously with those perceived as positive in the prediction of Time dependent variables. As regression equations were performed, α was limited to . for F-change statistics.

Results

On average, . life events (SD = .; range –) were reported in the months prior to the first inter-view. Of these life events, on average . (SD = .; range –) were rated by the informant as negative

events, and . (SD = .; range –) were viewed as positive events. The remainder were viewed as having no impact on the life of the adult with ID. Life events that were reported to occur in more than % of the sample included changes at work, in social activities and in recreation.

Concurrent analyses

Life events, as measured by total frequency, fre-quency of negative events and frequency of positive events, were not correlated with age or level of intel-lectual functioning of the adult with ID. No gender or ethnic differences were found among these three measures of life events. No significant covariates were identified for concurrent measures of behaviour problems or depressive symptoms.

Frequency counts of life events were significantly correlated with measures of behaviour problems as measured by the ABC total score and all but one of its subscales (r = .–., P < .), and by the SIB-R and its subscales (r = .–., P < .). The ABC stereotypy subscale approached statistical significance for being correlated with life events (r = ., P = .). Life events were correlated with depression subscales of the ADAMS (r = ., P < .) and ADD (r = ., P < .). Table pre-sents the correlations between life events, behaviour problems and depression, along with the means and standard deviations of the measures of these con-structs, and internal consistency measures where appropriate.

Frequency counts of life events perceived as nega-tive were significantly correlated with measures of behaviour problems as measured by the ABC total score and all of its subscales (r = .–., P < .), and by the SIB-R total score and all of its subscales (r = .–., P < .). Life events perceived as negative were correlated with depression subscales of the ADAMS (r = ., P < .) and ADD (r = ., P < .). The correlation between the ABC irritabil-ity subscale and life events viewed as negative was significantly stronger than the correlation between the ABC subscale and frequency counts of all life events, t() = ., P < . (Steiger ). No other cor-relations were found to be significantly different when comparing those obtained with life events viewed as negative with those obtained using frequency counts of all life events.




Frequency counts of life events perceived as positive were not correlated with measures of behaviour prob-lems as measured by the ABC or the SIB-R. How-ever, life events perceived as positive were correlated with depression subscales of the ADAMS (r = ., P < .) and ADD (r = ., P < .). Individuals experiencing more events perceived as positive were also reported to display elevated symptoms of depression.

To explore the relationship between depression and life events further, individuals with a diagnosis of depression in their current psychiatric record were compared with the rest of the sample (n = ) on measures of life events. Individuals with major depression were reported to experience more life events in the past months [t() = −., P < .], and more life events perceived as negative [t() = −., P < .]. No differences were found between individuals diagnosed with or without major depression on the number of life events perceived as positive [t() = −., P > .] (See Fig. ).

Prospective analyses

Hierarchical regression analyses were conducted to predict problem behaviours and depression from life

events reported at Time , controlling for Time measures of the dependent variables. The dependent variables of behaviour problems and depression were not correlated with the age or level of intellectual functioning of the individual being rated, and did not exhibit gender differences. Ethnic differences were found on the dependent variables of the SIB-R, with the exception of the SIB-R externalized subscale. Caucasians in the sample exhibited more general, internalized and asocial behaviour problems than African-Americans. Ethnicity was controlled for in analyses predicting these variables.

Life events served as a significant predictor of behaviour problems measured by the SIB-R general maladaptive index (F1,97 = ., P < .; ∆R2 = .) and its internalized (F1,97 = ., P < .; ∆R2 = .) and externalized subscales (F1,99 = ., P < .; ∆R2 = .), but not of the SIB-R asocial subscale, or of the ABC and its subscales (see Table ). Life events served as a significant predictor of depression as measured by the ADD (F1,83 = ., P < .; ∆R2 = .), but not by the ADAMS.

Life events viewed as positive and negative, reported at Time , were entered simultaneously in the prediction of Time problem behaviours and depression, controlling for the Time measures of

Table 1 Correlations between life events, behaviour problems and depression (n = )

MeasureFrequency oflife events

Negativelife events

Positivelife events Mean (SD) Alpha

Behaviour problemsABC irritability† 0.29** 0.49** 0.05 6.7 (8.2) 0.92ABC lethargy† 0.31** 0.38** 0.13 4.0 (5.4) 0.88ABC stereotypy† 0.19 0.33** 0.08 1.2 (2.4) 0.82ABC hyperactivity† 0.22* 0.34** 0.03 5.6 (6.9) 0.91ABC inappropriate speech‡ 0.29** 0.32** 0.17 1.9 (2.5) 0.78ABC total score† 0.33** 0.48** 0.10 19.5 (20.6) 0.96SIB-R internalized 0.30** 0.36** 0.18 4.9 (8.9) –SIB-R asocial 0.21* 0.34** 0.03 6.7 (10.7) –SIB-R externalized 0.24* 0.39** 0.05 1.2 (8.4) –SIB-R general 0.29** 0.44** 0.09 6.8 (9.1) –

DepressionADAMS depressed mood† 0.40** 0.53** 0.20* 3.3 (3.7) 0.83ADD depression§ 0.50** 0.42** 0.33** 2.3 (2.5) 0.75

Mean (SD) 2.6 (2.9) 0.8 (1.5) 1.3 (2.0) –

Missing data resulted in smaller cell sizes as indicated: †n = , ‡n = , §n = .ABC, Aberrant Behavior Checklist; ADAMS, Anxiety, Depression and Mood Scale; ADD, Assessment of Dual Diagnosis; SIB-R, Scales of Independent Behavior – Revised.*P < .; **P < ..




the dependent variables (see Table ). The addition of positive and negative life events added significantly to the prediction of behaviour problems measured by the SIB-R internalized maladaptive index (F2,96 = ., P < .; ∆R2 = .), but not the other

SIB-R subscales, or the ABC and its subscales. Neg-ative life events served as a significant individual pre-dictor for the SIB-R internalized maladaptive index (pr = ., P < .). Positive life events also served as a significant individual predictor for the SIB-R

Figure 1 Life events reported at Time forindividuals with or without a clinical diag-nosis of depression. *P < ..

0

1

2

3

4

5

Frequency of all life events Negative life events Positive life events

Num

ber

of e

vent

s re

port

ed

Depression (n=17)No depression (n=87)

*

*

Table 2 Summary of regression analyses predicting behaviour problems and depression from frequency counts of life events (n = )†‡

Dependent variable

Predictor

Ethnicity§Time 1variable

Frequency oflife events ∆∆∆∆R2

F-statistic

Behaviour problemsABC irritability 0.86** 0.03 0.00 F1,97 = 0.36ABC lethargy 0.74** −0.04 0.00 F1,97 = 0.40ABC stereotypy 0.56** −0.03 0.00 F1,97 = 0.14ABC hyperactivity 0.78** 0.06 0.00 F1,97 = 0.88ABC inappropriate speech 0.77** 0.01 0.00 F1,98 = 0.36ABC total score 0.80** 0.03 0.00 F1,97 = 0.17SIB-R internalized 0.19 0.56** 0.24** 0.05 F1,97 = 8.47**SIB-R asocial 0.20* 0.78** 0.11 0.01 F1,97 = 2.89SIB-R externalized 0.68** 0.20** 0.04 F1,99 = 8.26**SIB-R general 0.20* 0.74** 0.20** 0.04 F1,97 = 9.98**

DepressionADAMS depressed mood 0.76** 0.11 0.01 F1,98 = 2.03ADD depression 0.66** 0.31** 0.08 F1,83 = 14.78**

†Standardized beta coefficients presented in table.‡∆R2 and F-statistic presented for the addition of life events to regression analyses.§African-American = , Caucasian = .ABC, Aberrant Behavior Checklist; ADAMS, Anxiety, Depression and Mood Scale; ADD, Assessment of Dual Diagnosis; SIB-R, Scales of Independent Behavior – Revised.*P < .; **P < ..




internalized maladaptive index (pr = ., P < .). The addition of positive and negative life events added significantly to the prediction of the depression subscale of the ADD (F2,82 = ., P < .; ∆R2 = .), but not the ADAMS. Negative life events served as a significant individual predictor of depression on the ADD (pr = ., P < .). Positive life events did not.

Discussion

This study corroborated previous findings of associ-ations between life events and concurrent behaviour problems and depression among individuals with ID. Individuals who were reported by a respondent to have experienced more life events were also reported to exhibit more behaviour problems and more depressive symptoms. However, many of the life events that were reported by the respondent included events that were considered to have a positive impact on the life of the individual with ID. The relationship

between behaviour problems and life events per-ceived as positive or negative specific to the individual being rated was explored further. Positive life events were found not to be associated with behaviour prob-lems. However, the association between negative life events and behaviour problems was stronger than that found between all life events and behaviour prob-lems, but only statistically stronger for the irritability subscale of the ABC. When examining the concurrent association between behaviour problems and life events, it does not appear that differentiating between life events in general or life events as perceived as negative had a large impact on statistically significant findings. Both frequency counts of life events and those events perceived as negative were associated with elevated levels of behaviour problems. Yet, in measuring negative life events among individuals with ID, precision may be increased if the life events are rated as positive or negative specific to the indi-vidual being rated rather than all events being labelled as negative by the researcher.

Table 3 Summary of regression analyses predicting behaviour problems and depression from negative and positive life events (n = )†‡§

Dependent variable

Predictor

Negativelife events

Positivelife events ∆∆∆∆R2 F-statistic

Behaviour problemsABC irritability 0.03 −0.04 0.00 F2,96 = 0.28ABC lethargy −0.06 −0.02 0.00 F2,96 = 0.42ABC stereotypy −0.06 0.03 0.00 F2,96 = 0.30ABC hyperactivity 0.08 −0.06 0.01 F2,96 = 0.87ABC inappropriate speech 0.08 −0.08 0.01 F2,97 = 1.17ABC total score 0.03 −0.04 0.00 F2,96 = 0.27SIB-R internalized 0.19* 0.16* 0.07 F2,96 = 5.70**SIB-R asocial 0.00 0.00 0.00 F2,96 = 0.69SIB-R externalized 0.14 0.10 0.03 F2,98 = 3.21*SIB-R general 0.12 0.11 0.03 F2,96 = 4.11*

DepressionADAMS depressed mood 0.09 −0.11 0.02 F2,97 = 2.03ADD depression 0.29** 0.08 0.10 F2,82 = 8.59**

†Standardized beta coefficients presented in table.‡∆R2 and F-statistic presented for the addition of negative and positive life events to regression analyses.§All analyses controlled for the Time measures of the dependent variables (and ethnicity for three measures of the SIB-R). Beta coefficients for these variables match those presented in Table .ABC, Aberrant Behavior Checklist; ADAMS, Anxiety, Depression and Mood Scale; ADD, Assessment of Dual Diagnosis; SIB-R, Scales of Independent Behavior – Revised.*P < .; **P < ..




Negative and positive life events were also exam-ined further in relation to concurrent depression. The association between negative life events and depres-sion was statistically significant as was the association between positive life events and depression. As more negative or positive life events were reported, more symptoms of depression were also reported. The cur-rent findings indicate that both positive and negative life events are potentially associated with elevated concurrent depressive symptomatology in adults with ID.

To clarify the association between concurrent depression and life events, individuals with a clinical diagnosis of depression were compared with those without a diagnosis of depression. Individuals with major depression were reported to experience a sig-nificantly greater frequency of all life events and of negative life events in the prior months. However, they did not differ from controls on the frequency of positive life events. Thus, the correlation between depression and positive life events is not substanti-ated at clinical levels. It is important to note that the elevated frequency of negative life events for individuals with clinical depression was provided by informant-reports. Thus, the elevated frequency cannot be attributed to depressed individuals with ID perceiving events as negative, although it is still possible that depressed individuals interact with their environment in such a way to influence the occurrence of negative events.

The current study expanded upon previous inves-tigations with its prospective design. Prior work had been unable to determine the causal nature of the relationship between life events and behaviour prob-lems or depression. The current data indicate that when controlling for past levels of behaviour prob-lems, life events served as a significant predictor when using the SIB-R, but not when using the ABC. Although the frequency of life events was correlated with the ABC and its subscales, it was not a causal predictor of behaviour problems as measured by the ABC. This finding indicates that the causal relation-ship between life events and behaviour problems is dependent upon the scale and subscales selected to measure various behaviour problems. We hypothesize that this may result from the instructions provided to the informants for the ABC and the SIB-R. The stan-dard instructions for the ABC refer to behaviours over the last weeks, whereas the SIB-R addresses

any behaviour problem over the -month interval of the study. As such, ratings using the ABC may not have been sensitive to behaviour problems in the intervening months that may have arisen from the reported life events.

In regards to behaviour problems measured by the SIB-R, only the frequency of life events served as a causal predictor of general and externalized behav-iour problems. This finding indicates that although the frequency of life events and life events perceived as negative are correlated with asocial behaviour problems, they are not causal predictors of this behaviour problem. This finding also indicates that, with the current sample, frequency of life events served as a causal predictor, whereas distinguishing between negative and positive life events did not add to the causal prediction of general or externalized behaviour problems. Conversely, all three measures of life events were causal predictors of internalized behaviour problems measured by the SIB-R. This indicates that any change in the life of the adult with ID is a potential causal predictor of internalized behaviour problems as measured by the SIB-R, even though positive life events are not concurrently related to this construct.

As internalized behaviour problems and depression are related constructs, one would expect that any change in the life of the individual with ID would also be related to subsequent elevations of depressive symptoms. However, when controlling for past levels of depressive symptoms, only the frequency of life events and life events perceived as negative served as significant predictors of the depression subscale of the ADD. Positive life events did not serve as a causal predictor, and no measure of life events served as a causal predictor of the depression subscale of the ADAMS. While consistent findings would be expected as the depression subscales of the ADD and ADAMS are highly correlated (r = .), it should be noted that individuals were not rated on the ADD, of which approximately two-thirds had severe ID. As the ADD is intended only for individuals with mild or moderate ID, it was not completed for individuals with lower levels of intellectual functioning. As such, with a higher-functioning group, both frequency counts of life events and life events perceived as neg-ative served as significant predictors of subsequent depressive symptomatology. And with a group including lower-functioning individuals rated on the




ADAMS, the predictive ability did not hold. This is consistent with the findings of Ghaziuddin () where life events played a larger role among higher-functioning individuals with ID.

There are several limitations of the current study that should be noted. First, the current study only included life events from the previous months. This length of time is shorter than other studies on the association between life events and depression or behaviour problems. The shortened length of time did not appear to have an impact on concurrent anal-yses, and the strength of the association between life events and depression or behaviour problems is com-parable with other published findings with longer time intervals. But the shortened time period may have had an impact on prospective analyses by not capturing events that may have been causal in the development of behaviour problems or symptoms of depression.

Second, the LES is not specific to individuals with ID. As such, it may not have captured additional life stressors such as changes in staff. However, open-ended questions at the end of the LES often identi-fied such stressors. An informant-report instrument specific to individuals with ID, such as the Life Events List, may be more appropriate for assessing stressors in the lives of individuals with ID (Owen et al. ). However, such an instrument could be benefited by including a rating of whether the impact of the event was considered positive or negative. Third, the impact ratings of the life events required the subjective judgement of the informant regarding how the individual with ID perceived the life event. Relying on informants to rate the perception of others has been brought into question in the quality of life research (Stancliffe ), and likewise also applies here. Future researchers are encouraged to obtain self- and informant-reports of life events for the individual with ID.

The current findings have numerous implications for the development of depression or behaviour problems among individuals with ID. First, researchers and clinicians are encouraged to have the rater assess whether a life event is viewed as positive or negative rather than developing an ‘a priori’ list of negative events. Depending on the situation, what a researcher considers a negative event could be a positive event for the specific individual being rated. Although measuring all life

events was predictive of more measures of behav-iour problems than was life events perceived as negative, it may be more precise to determine rat-ing of the impact of the event on the individual. Where appropriate to the individual being rated, it may be even more accurate to obtain the individ-ual’s perception of the event using self-report mea-sures (Bramston & Fogarty ; Esbensen & Benson in press). Second, researchers need to be aware that the outcome of predicting behaviour problems and depression from life events can be influenced by how a construct is measured and the instructions provided with the instrument. Future researchers examining the relationship between these constructs should be aware that their find-ings may be due to measurement issues and are encouraged to use multiple measures of each construct. And third, there is indication that both frequency counts of life events and life events perceived as negative are related to the prospective development of depression and behaviour prob-lems, although as mentioned previously, measure-ment issues play a role in the findings. The current results are in need of replication with different and multiple ratings of the dependent measures.

The association between life events and behaviour problems or depression has been examined by sev-eral researchers. But the causal association between the constructs was undetermined. The current study provides preliminary evidence that life events in gen-eral are causal in the development of general, inter-nalized and externalized behaviour problems, and that life events perceived as negative or positive are causal in the development of internalized behaviour problems. However, this preliminary finding is only supported when measuring behaviour problems with the SIB-R and not with the ABC over a -month interval. In addition, it appears that life events in general and negative life events predict the develop-ment of depressive symptoms among individuals with higher-functioning levels of ID. The finding that life events can be causal with some measures of behaviour problems or depressive symptoms should not be ignored. Given replication of the current find-ings with other measures of these constructs, pre-ventative efforts should be made to intervene after the experience of life events to potentially reduce or mitigate symptoms of depression and behaviour problems.




Acknowledgements

This research was supported in part by grants from the Ohio Department of Mental Health (#.) and the National Institute on Child Health and Development (T HD, P HD), and by the Ohio State University Alumni grant for Grad-uate Research & Scholarship.

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A prospective analysis of life events, problem behaviours and depression in adults with intellectual disability