Clinical Profile of Clients in a Specialized Dual Diagnosis Program: Comparison of Individuals with and without ASD

Background: The term “dual diagnosis” is commonly used to describe individuals with an intellectual or developmental disability (including Autism Spectrum Disorder [ASD]) and a psychiatric diagnosis.  Studies have found elevated levels of psychopathology in individuals with ASD when compared to individuals with intellectual disabilities who do not have ASD.  Persons with ASD have been found to be more likely to have comorbid psychiatric diagnoses, more problem behaviours, and increased use of psychotropic medications (Morgan, Roy & Chance, 2003; Bradley & Bolton, 2006; Bradley, Summers, Wood & Bryson, 2004; Brereton, Tonge & Einfeld, 2006; Tsakanikos et al., 2007).  These findings, however, are not universal (i.e., Tsakanikos et al., 2006), and may not hold true for individuals in our clinical (as opposed to community) sample, the majority of whom come in to the program with an existing psychiatric diagnosis.  Nevertheless, it may be that individuals with ASD in specialized “dual diagnosis” programs present with more severe psychopathology and more behavioural challenges than individuals with an intellectual disability only.  Palucka and Lunsky (2007) and Prichard et al. (2007) have described characteristics of clients with ASD in a tertiary level “dual diagnosis” program.  However, a more detailed comparison of the diagnostic and behavioural profiles of dually diagnosed clients with and without ASD has not been conducted.   
Objectives: The present study sought to expand upon the findings of previous research by comparing the clinical profiles of clients with and without ASD referred to a “dual diagnosis” psychiatry service for individuals with intellectual disabilities.  In particular, we analyzed differences in demographics, psychopathology, medication use, and behavioural symptomatology, as assessed using the Aberrant Behaviour Checklist (ABC) and Reiss Screen for Maladaptive Behaviour. 
Methods: We reviewed the charts of a subset of clients (n = 74) who received services from a specialized “dual diagnosis” program from 2006 to 2008.  The sample was subdivided into an ASD (n = 21) and a non-ASD (n = 53) group, based on the diagnosis at the time of admission.  For all clients, the ABC and Reiss were completed by caregivers within one month of beginning service. 
Results: Demographically, there were more men in the ASD group (χ² (1,74) = 8.90,  p < 0.01), with no other differences terms of ethnicity, age, or residential setting.  Clinically, clients with and without ASD did not differ in their psychotropic mediation use, or Reiss and ABC scores, with the exception of higher scores for the ASD group on the autism (t(71) = 2.28, p < 0.05) and psychosis (t(71)=2.19, p < 0.05) subscales of the Reiss.  Diagnostically, there was a trend towards lower rates of mood disorders in the ASD group (χ² (1,74) = 3.32,  p = 0.07).
Conclusions: Contrary to the findings of previous research, individuals with ASD in this clinical sample exhibited the same range of psychopathology and maladaptive behaviour as other individuals, according to caregiver ratings.  Future research with a larger client sample is needed to further refine the psychiatric profile of individuals with ASD.  Interpretation and implications of the findings are discussed.