The Psychopathology in Autism Checklist (PAC): A pilot study

https://doi.org/10.1016/j.rasd.2008.05.004Get rights and content

Abstract

Adults with autism and intellectual disability (ID) are assumed to have high vulnerability for developing psychiatric disorders, but instruments or criteria for identifying those who may be in need of psychiatric services have been lacking. This study presents a new carer-completed screening checklist designed for this purpose.

Differentiation between symptoms related to autism and to psychiatric disorders is indicated in order to identify psychiatric disorders in persons with autism. The Psychopathology in Autism Checklist (PAC) contains 30 items representing symptoms previously evaluated as specific to one of four major psychiatric disorders (psychosis, depression, anxiety and OCD) and not related to autism. Twelve items evaluated as indicators of general adjustment problems are also included. All 42 items are based on ICD-10 and DSM-IV criteria.

The PAC was piloted on a sample of 35 adults with autism and ID. The score of participants previously identified with co-occurring psychiatric disorders (i.e. psychosis, depression, anxiety disorder, or OCD) were compared with the score of participants without psychiatric disorders.

The results indicate acceptable psychometric properties, and that the PAC discriminates between adults with autism and ID with and without psychiatric disorders, and partially between individuals diagnosed with different psychiatric disorders.

Introduction

Adults with autism and intellectual disability (ID) are assumed to have higher vulnerability for developing psychiatric disorders than the general population (Clarke, Baxter, Perry, & Prasher, 1999; Ghaziuddin, 2005; Lainhart, 1999). The process of diagnosing mental health disorders in this population is, however, complex and challenging, and related to at least four fundamental problems: (1) the overlap of symptoms between autism and psychiatric disorders (Clarke et al., 1999; Clarke, Littlejohns, Corbett, & Joseph, 1989; Ghaziuddin, Alessi, & Greden, 1995; Ghaziuddin, Tsai, & Ghaziuddin, 1992; Kobayashi & Murata, 1998; Lainhart, 1999; Long, Wood, & Holmes, 2000; McDougle, Kresch, & Posey, 2000; Reaven & Hepburn, 2003; Volkmar & Cohen, 1991; Wing, 1996); (2) idiosyncratic or atypical psychiatric symptoms (Lainhart, 1999; Myers & Winters, 2002; Stavrakiki, 1999; Tantam, 2000); (3) reduced capacity for introspection and problems communicating their personal state (Ghaziuddin, 2005; Howlin, 1997; Lainhart, 1999); and (4) the lack of standardized instruments or criteria for diagnosing psychiatric disorders in this group(Ghaziuddin, 2000; Howlin, Goode, Hutton, & Rutter, 2004; Lainhart, 1999; Matson & Nebel-Schwalm, 2007; Tsai, 1996).

The present study represents a new approach and an attempt toward solving these fundamental and practical problems related to the identification of individuals with psychiatric disorders in this population. The possibility of differentiating between symptoms related to autism and to four major psychiatric disorders has previously been demonstrated (Helverschou, Bakken, & Martinsen, 2008). The Psychopathology in Autism Checklist (PAC) is based on these results, and contains indicators of psychiatric disorders that do not overlap with the core characteristics of autism. In the present study the assessment of typical individuals with autism, ID and different psychiatric disorders is addressed.

The overlap of symptoms between autism and psychiatric disorders is considerable (Clarke et al., 1989, Clarke et al., 1999; Ghaziuddin et al., 1995, Ghaziuddin et al., 1992; Kobayashi & Murata, 1998; Lainhart, 1999; Long et al., 2000; McDougle et al., 2000; Reaven & Hepburn, 2003; Volkmar & Cohen, 1991; Wing, 1996). Similar behaviors may be indicators of both autism and a psychiatric disorder. For example, the ritualistic and repetitive behaviors that are defined as core characteristics of autism may also be expressions of obsession (Ghaziuddin, 2005; Scahill et al., 2006), and lack of social interaction may be interpreted both as a feature of autism and as a symptom of schizophrenia (Konstantareas & Hewitt, 2001).

The confounding of symptoms of autism and psychiatric disorders is further illustrated by the extensive variation in reported prevalence rates of psychiatric disorders in individuals with autism (Lainhart, 1999). Howlin (2000) reported, for example, a variation between 9 and 89%. The variety in prevalence rates may be related to the characteristics of the clinical populations studied and the disorders targeted by the studies. However, the different assessment methods and diagnostic criteria that were employed in the studies seem to be essential to the wide variation in reported prevalence rates (Bradley, Summers, Hayley, & Bryson, 2004; Howlin, 2000; Lainhart, 1999). Several researchers have therefore addressed the need for standardized instruments or criteria for diagnosing psychiatric disorders in individuals with autism (Ghaziuddin, 2000; Howlin et al., 2004; Lainhart, 1999; Matson & Nebel-Schwalm, 2007; Tsai, 1996).

Idiosyncratic and atypical psychiatric symptoms have frequently been reported in case studies of individuals with autism (Lainhart, 1999; Myers & Winters, 2002; Stavrakiki, 1999; Tantam, 2000). Challenging behavior like self injury and aggressive behavior have been reported as signs of depression (Myers & Winters, 2002). Likewise, more intense ruminations and an increase in typical autism symptoms like repetitive and ritualistic behavior have been described when individuals with autism develop psychiatric disorders (Tantam, 2000; Wing, 1996).

Psychiatric diagnoses are usually and mainly based on an interview with the person or self-rating checklists. Individuals with autism and ID have reduced capacity for introspection and problems communicating their personal state, which further complicate the diagnostic process and indicate the use of other sources, i.e. informants or observation. In published case stories the diagnostics has been based on identifying qualitative changes in long-standing symptomatology in the individual's premorbid features of autism, conventional diagnostic criteria related to specific disorders, and the interpretation of idiosyncratic or atypical symptoms (e.g. Ghaziuddin, 2005; Lainhart, 1999). There seems to be a general agreement that an accurate diagnostic assessment depends on distinguishing between symptoms that are representing the autistic condition and symptoms that are representing other psychiatric conditions (Ghaziuddin, 2005; Lainhart, 1999; Tsai, 1996).

Studies of two new instruments designed for identifying individuals with autism and psychiatric disorders have recently been published; the Autism Co-morbidity Interview—Present and Lifetime version (ACI-PL, Leyfer et al., 2006) and the Autism Spectrum Disorder—Comorbidity for Adults (ASD-CA; Matson & Boisjoli, 2008). According to the authors, the ACI-PL is designed to distinguish impairment due to co-morbid psychiatric disorders from impairment due to the core features of autism. However, both the authors and critiques have pointed out that some of the symptoms may represent both the co-morbid diagnoses and autism (Minshew, 2006), indicating that the instrument has not fully succeeded in differentiating between autism symptoms and symptoms of psychiatric disorders. The ASD-CA is constructed to assess co-morbid psychopathology in adults with ASD and ID, and contains items judged by the authors as characteristic of the most probable additional disorders in the ASD population. Differentiating between symptoms related to autism and symptoms related to the psychiatric disorders does not seem to have been an explicit aim in the development of the ASD-CA, and for the present, only psychometric properties have been reported.

Another approach was chosen in the development of the Psychopathology in Autism Checklist (PAC). The development of the PAC is based on the understanding that differentiating between autism and psychiatric disorders is a prerequisite for developing more accurate and reliable psychiatric diagnoses in this group. In a previous study, it was demonstrated that a panel of clinicians were able to identify symptoms of four major psychiatric disorders that do not overlap with the core characteristics of autism (Helverschou et al., 2008). These items are considered as indicators of psychiatric disorders in individuals with autism and ID and were included in the PAC. They are related to four major psychiatric disorders: psychosis, depression, anxiety disorder and obsessive-compulsive disorder (OCD). The PAC is a carer-completed screening checklist for the identification of individuals with autism and ID in need of psychiatric services. Care staff and family may be the best option for reporting on changes in relation to premorbid or typical pattern of behavior and mood and to give information on idiosyncratic or atypical psychiatric symptoms (Bradley et al., 2004; Howlin, 1997; Lainhart, 1999; Matson & Boisjoli, 2008).

Assessing clients with previously identified psychiatric disorders was chosen for the first empirical test of the PAC because it is a well-known method for validating psychometric instruments (Matson, Gardner, Coe, & Sovner, 1991; Moss et al., 1998). Adults with autism and ID previously identified with co-occurring psychiatric disorders (i.e. psychosis, depression, anxiety disorder, or OCD) were compared with adults with autism and ID without psychiatric disorders. The main questions were firstly whether the PAC distinguishes between individuals with autism and ID with and without psychiatric disorders, and secondly whether it distinguishes between individuals with different co-morbid psychiatric disorders.

Section snippets

Participants

A sample of 47 adults previously or presently registered as clients by the specialized health services at Ullevål University Hospital in Oslo, Norway was recruited to the study (see Bakken, Friis, Lovoll, Smeby, & Martinsen, 2007). The aim was to include typical representatives of their diagnosis; for having autism and ID and different co-occurring psychiatric diagnoses or for having autism and ID and not a psychiatric disorder. The diagnoses of autism, intellectual disability and psychiatric

Results

The average scores on the five subscales of the PAC were used to examine the differences between the subgroups (see Table 3). The average scores of the nine individuals with autism and ID without psychiatric diagnoses, the “autism only group”, were between 1.2 and 1.4, and the lowest on all subscales. The average scores of the four psychiatric subgroups ranged from 1.9 to 3.1. The overall differences between all five subgroups computed by Kruskal–Wallis Test were found to be statistically

Discussion

All psychiatric subgroups obtained significantly higher average scores on all subscales than the non-psychiatric group, which indicate that all the subscales seem to discriminate well between individuals with autism and ID with and without psychiatric diagnoses. Thus, the results of the present study demonstrate that by using indicators of psychiatric disorders that do not overlap with the core characteristics of autism, it is possible to differentiate between individuals with autism and ID who

Acknowledgements

The project is funded by, and part of, a program established by The National Autism Unit at the Rikshospitalet University Hospital in Oslo and the former National Autism Network of Norway with the objective of ensuring necessary services for adults with autism, intellectual disability and psychiatric disorders. The project represents a joint venture between Ullevål University Hospital in Oslo and the National Autism Unit. The participants in the pilot study were recruited by two departments at

References (66)

  • L.E. Alden et al.

    Social anxiety as a clinical condition: I

  • American Psychiatric Association

    Diagnostic and statistical manual of mental disorders

    (1994)
  • T.L. Bakken et al.

    Behavioral disorganization as an indicator of psychosis in adults with intellectual disability and autism

    Mental Health Aspects of Developmental Disabilities

    (2007)
  • P. Bech et al.

    Scales for assessment of diagnosis and severity of mental disorders

    Acta Psychiatrica Scandinavica

    (1993)
  • E.A. Bradley et al.

    Comparing rates of psychiatric and behaviour disorders in adolescents and young adults with severe intellectual disability with and without autism

    Journal of Autism and Developmental Disorders

    (2004)
  • D. Clarke et al.

    The diagnosis of effective and psychotic disorders in adults with autism: seven case reports

    Autism

    (1999)
  • D.J. Clarke et al.

    Pervasive developmental disorders and psychoses in adult life

    British Journal of Psychiatry

    (1989)
  • J.D. Coplan et al.

    A view on noradrenergic, hypothalamic–pituitary–adrenal axis and extra hypothalamic corticotrophin-releasing factor function in anxiety and affective disorders: The reduced growth hormone response to clonidine

    Psychopharmacology Bulletin

    (1997)
  • L. Crocker et al.

    Introduction to classical and modern test theory

    (1986)
  • W.C. Dreves et al.

    Depression, mania and related disorders

  • E. Emerson et al.

    The relationship between challenging behaviour and psychiatric disorders in people with severe developmental disabilities

  • M. Gelder et al.

    New Oxford textbook of psychiatry

    (2003)
  • M. Ghaziuddin

    Autism and mental retardation

    Current Opinion in Psychiatry

    (2000)
  • M. Ghaziuddin

    Mental health aspects of autism and Asperger syndrome

    (2005)
  • M. Ghaziuddin et al.

    Life events and depression in children with pervasive developmental disorders

    Journal of Autism and Developmental Disorders

    (1995)
  • M. Ghaziuddin et al.

    Comorbidity of autistic disorder in children and adolescents

    European Child and Adolescent Psychiatry

    (1992)
  • C. Gustafsson et al.

    Occurrence of mental health problems in Swedish samples of adults with intellectual disabilities

    Social Psychiatry and Psychiatric Epidemiology

    (2004)
  • Helverschou, S. B., Bakken, T. L., & Martinsen, H. (2008). Identifying symptoms of psychiatric disorders in people with...
  • C. Hemmings

    The relationships between challenging behaviours and psychiatric disorders in people with severe intellectual disabilities

  • P. Howlin

    Autism: Preparing for adulthood

    (1997)
  • P. Howlin

    Outcome in adult life for more able individuals with autism or Asperger syndrome

    Autism

    (2000)
  • P. Howlin et al.

    Adult outcome for children with autism

    Journal of Child Psychology and Psychiatry

    (2004)
  • J.A. Kim et al.

    The prevalence of anxiety and mood problems among children with autism and Asperger syndrome

    Autism

    (2000)
  • Cited by (0)

    View full text