Psychiatric Co-Morbidity Among Adults with Autism Spectrum Disorder

Background:  Understanding the presence of co-morbid psychiatric disorders has important implications for our understanding of adult outcomes and service needs for individuals with autism spectrum disorders (ASD). Several studies have found high rates of co-morbid psychiatric conditions among children and adolescents with ASD. Unfortunately, the frequencies of these conditions have not yet been established in a representative sample of adults.  Studies of children and adolescents with autism have shown high rates of Axis I psychiatric co-morbidity, frequently involving more than one disorder.  Results among adult studies have been variable, although most find that depression and anxiety are common, particularly in individuals with high functioning autism or Asperger’s Disorder.  Yet, some studies suggest that the higher incidence of co-morbid psychiatric disorders found in children with autism does not persist into adulthood.  Thus, a comprehensive assessment of current functioning and important characteristics outside the realm of ASD diagnostic criteria is critical to our understanding of the natural course and ultimate outcome of adults with ASD. The Mini PAS-ADD Interview assesses Axis I psychiatric disorders.  There is no one tool that has established validity, reliability, and cut-off scores for this use in adults with autism across the spectrum of intellectual ability.  The Mini PAS-ADD is a reliable and valid tool for use in adults with intellectual disabilities (ID) and identifies seven subscales of Axis I co-morbidity based on the ICD-10 diagnostic algorithms of the Schedules for Clinical Assessment in Neuropsychiatry (SCAN). 

Objectives:  This study examines adults with ASD to (1) determine the presence of co-morbid psychiatric disorders and (2) identify the patterns of psychiatric symptoms and disorders affecting this population-based adult ASD sample.   

Methods:  As part of a large adult outcomes study, individuals with ASD (and their caregivers) ascertained during a 1980’s state-wide Utah autism epidemiological study participated in a semi-structured interview querying the current and lifetime presence of psychiatric symptoms.  The Mini PAS-ADD Interview was administered to caregivers of 132 participants between the ages of 24 and 54 with either DSM III autism (N= 107) identified in the original study or DSM-IV-TR autism spectrum disorder (N= 25), identified during a reclassification study.   We applied the established cut-off scores to determine case definition for each disorder.       

Results: Of the 132 participants, 73 (55%) met the case definition for a current co-morbid psychiatric disorder and 92 (70%) for a lifetime co-morbid psychiatric disorder.   The most frequently experienced co-occurring psychiatric disorder for both current and lifetime conditions was Anxiety Disorder, [N = 51 (39%) and 70 (53%), respectively].  Obsessive-Compulsive Disorder was also quite common, affecting 43 (33%) participants currently and 48 (36%) participants during their lifetime.  Other co-occurring psychiatric disorders, current and lifetime respectively, were Depressive Disorder [1 (1%), 17 (13%)], Expansive Mood [2 (2%), 8 (6%)], and psychosis [6 (5%), 13 (10%)]. 

Conclusions:  Co-morbid psychiatric disorders occur frequently in adults with ASD.  Using standard criteria, adapted for individuals with intellectual disability, is an effective means of identifying psychiatric disorders in this population.