Understanding Comorbid Conditions in Children and Adolescents with ASD

Background:  

Little previous research has been aimed at understanding the prevalence and changing nature of comorbid conditions in children with Autism Spectrum Disorders (ASD) as they age. Research suggests that there are high rates of comorbid conditions present (Bruin, Ferdinand, Meester, Nijs, & Verheij, 2006; Kim, Szatmari, Bryson, Streiner, & Wilson, 2000; Lainhart, 1999), however, sample sizes have been limited and  the range of psychiatric comorbidities examined has been limited primarily to depression (Ghaziuddin, Ghaziuddin, & Greden, 2002), anxiety (Kim et al., 2000), or attention deficit/hyperactivity disorder (Gillberg & Billstedt, 2000). A comprehensive evaluation of several comorbid conditions, how they change with age and comparisons to typically developing groups has not been reported and there are few tools to assess these changes. Pandolfi, Magyar, and Dill (2012) reported an initial assessment of multiple symptoms using the Child Behavior Checklist 6-18 (CBCL) (Achenbach & Rescorla, 2000, 2001), which provided a preliminary account of co-morbid problems in older adolescents, but also suffered from many of the same issues as previous papers.

Objectives:  

(1) Determine the overall prevalence of comorbid symptoms in children and adolescents with ASD and the overall amount of comorbidities, and (2) assess possible trends in comorbid conditions when comparing age and gender cohorts to see how these develop over time and assess prevalence of symptoms compared to age matched typically developing siblings.

Methods:  

Subjects with ASD as well as typical siblings were recruited from the Simons Simplex Collection and the Boston Autism Consortium.  All consenting participants received a comprehensive diagnostic assessment including an Autism Diagnostic Observation Schedule (ADOS), the Autism Diagnostic Interview-Revised (ADI-R), cognitive, language, behavioral and adaptive skills assessments.  To assess symptom presentation, the two forms of the Child Behavior Checklist were used (1.5-5 years of age and 6-18 years of age). There is overlap in several subscales that allow for direct age and gender cohort comparisons to determine how aging and gender affects these symptoms. The Syndrome subscales of interest were: aggression, attention, somatic, withdrawn/depressed and anxious/depressed symptom groups. Scores on these subscales were categorized into groups based on the clinical cutoff scores:  below threshold, borderline, or above clinical cutoff.

Results:  

To date, we have enrolled 2851 individuals (from 2842 families). Individuals with ASD ranged in age from 3 to 18 years, and had a mean IQ of 84.4 (SD = 26.3).  The most common elevated (i.e. above clinical cutoff) subscales on the CBCL 6-18 were Thought Problems, Attention Problems and Withdrawn/Depressed; CBCL 2-5 common elevations were Withdrawn, Attention Problems and Emotionally Reactive with this trend continuing when controlling for IQ.  Significant elevations were not different between males and females with the exception of the Attention subscale, on which males scored higher than females. Analysis of DSM scales, longitudinal data and comparisons to sibling control groups is ongoing. 

Conclusions:  

Co-morbid symptoms among individuals with ASD were extremely common, with 1867 (65.5%) participants surpassing the clinical cutoff on the syndrome scales of the CBCL. Analyses are ongoing for comparisons with typical siblings.