Psychopathology and Intellectual Disability: The Australian Child to Adult Longitudinal Study

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Publisher Summary

This chapter discusses the different aspects of psychopathology and intellectual disability (ID). ID is a serious handicap in itself and, however, the problem is compounded significantly when complicated by emotional and behavioral problems. Psychopathology is not only the most common complication associated with ID but also carries the most critical consequences. The psychopathology associated with ID can be described by adopting either a top-down approach, using diagnostic categories, derived from traditional psychiatric taxonomies. The success of the longitudinal study is dependent on the participation of the young people and their families. Considerable effort has been expended to keep in touch with the families and track them if they move. Assessments were made of various risk and protective variables potentially associated with psychopathology. The intellectual ability of each child was assessed from the records of psychological assessments or when the child was evaluated directly, using an appropriate standard cognitive assessment. The study has produced evidence that the genetic cause of ID has an impact on the levels and patterns of psychiatric disturbance.

Section snippets

The Added Burden of Behavioral and Emotional Problems in Intellectual Disability

Intellectual disability (ID) is a serious handicap in itself; however, the problem is compounded significantly when complicated by emotional and behavioral problems. Psychopathology is not only the most common complication associated with ID but also carries the most critical consequences. Indeed, families with children with ID rate behavior problems as a much higher source of stress than the constant demands of a profoundly handicapped and totally physically dependent child (Quine & Pahl, 1985

The Phenomenology of Behavioral and Emotional Disturbances in Intellectual Disability

The psychopathology associated with ID can be described by adopting either a top-down approach using diagnostic categories derived from traditional psychiatric taxonomies such as DSM (American Psychiatric Association, 1994) and ICD (World Health Organization, 1992) or a bottom-up taxonometric approach as a description of individual behaviors and emotions or symptoms. Modifications to existing classification systems are undergoing development to take into account the modifying effect of ID.

Etiology of Dual Disability

Psychopathology in ID is likely to be caused by a complex interaction of factors. Biological factors that affect brain function such as tuberous sclerosis, the behavioral phenotype of some genetic disorders such as Williams syndrome (WS) (Einfeld, Tonge, & Florio, 1997), fragile X syndrome (Einfeld, Tonge, & Florio, 1994) and Prader–Willi syndrome (PWS) (Einfeld, Smith, Durvasula, Florio, & Tonge, 1999), and heritable temperamental characteristics are associated with behavior problems.

The Australian Child to Adult Longitudinal Study

The primary aim of this study is to determine the predictors and patterns of psychopathology in a representative population of young people with ID over time. In 1989/1990, a comprehensive attempt was made to identify all young people aged 4–18 years with ID who lived in a number of geographically defined regions in the Australian states of New South Wales and Victoria (Einfeld & Tonge, 1996a). These regions were local government areas, which together represented a cross section of the

Longitudinal Study Measures

The study gathered data on a broad range of potential biopsychosocial risk and protective variables, including causes of ID, and measures of life events, parental mental health, and family functioning in 1991/1992 (Time 1), 1996/1997 (Time 2), and 1999/2000 (Time 3). The major measure of psychopathology was the DBC (Einfeld & Tonge, 1992). The DBC has 96 items completed by the parents or other primary carers reporting problems with emotions or behavior over a 6-month period. The instrument has

Prevalence Of Psychopathology

At time 1 (1991–1992), the average age of the sample was 12.1 years. Within the epidemiological sample, the proportion of those classified as a “psychiatric case,” i.e., with DBC total scores above the cutoff score of 46, was 43.3% Einfeld 1996a, Einfeld 1996b. Approximately 9 years later (Time 3 M age = 19.4), 36.7% of the sample were classified as a “case,” indicating that there was a significant reduction in the overall prevalence of psychiatric disturbance (χ2 = 7.317, p < .05). Of those

Biological Risk Factors

The study has produced evidence that the genetic cause of ID has an impact on levels and patterns of psychiatric disturbance. Young people with autism, Prader–Willi syndrome, or fragile X syndrome showed higher overall levels of psychopathology compared to the epidemiological sample (see FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6 and Table IV for confidence intervals). When the Down syndrome subset of the epidemiological sample was compared with the remainder of the epidemiological sample,

Cognitive Ability

The level of cognitive ability had some effect on the pattern of psychopathology. Those with moderate and more severe levels of ID had more self-absorbed behaviors and social relating difficulties, whereas those with milder levels of ID tended to have more antisocial disruptive behaviors. The level of ID also had some influence on the patterns of behavior in children with autism as reported earlier. The cognitive profile, with its indication of relative strengths and weaknesses, is relevant to

Social And Family Factors

The study produced evidence that family factors are associated with, and predict, psychopathology. Further follow-up is needed to determine if there is a predominant direction to this association, although the clinical impression is that emotional and behavioral problems in young people with ID are a great stress on the family and may compromise parental mental health and family function.

Prediction Of Psychopathology In Young People With Intellectual Disability

The availability of a range of biopsychosocial data collected at Time 1 (1991/1992) and again at Time 2 (1995/1996) provides some capacity to begin to examine factors that might influence and predict the development and maintenance of psychopathology, and any influences protective of mental health in this vulnerable population. Considerably more power of prediction will be gained when data from subsequent Time 4 and further waves of data collection are obtained. The predictive capacity of data

Conclusions

The longitudinal and associated syndrome group studies have produced considerable evidence to confirm that serious psychopathology in young people with ID is at least two to three times more common than in the general population and tends to persist from childhood through adolescence into early adult life. Approximately 15% of disturbed young people recover their mental health over time, but a similar proportion of young people develop serious mental health problems. Some psychopathology such

Acknowledgments

The studies reported here were supported in part by the National Health and Medical Research Council, Australia. The authors acknowledge the contribution of participating families. The ACAD project would not have been possible without its dedicated research staff. A full list of staff names is available at //www.med.monash.edu.au/psychmed/units/devpsych/acad.html.

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