Prevalence of and Associations with Co-Morbid Psychiatric Symptoms in Children with ASD in an Urban Elementary School District

Background: The reported prevalence rates of co-occurring psychiatric symptoms and disorders in children with autism spectrum disorders (ASD) has varied widely. Relatively little research has investigated these rates in ethnically diverse community samples. Previous research findings differ as to whether associations exist between psychiatric symptoms and other characteristics of children with ASD, such as autism severity, IQ, age, gender, and ethnicity (Gadow et al., 2005; Gadow et al., 2008; Lecavalier, 2006; Simonoff et al., 2008).

Objectives: 1) to examine the prevalence of co-morbid psychiatric symptoms in an urban community sample of children with ASD; and 2) to examine the associations among child characteristics and co-morbid psychiatric symptom severity in this sample.

Methods: Children in kindergarten-to-second grade autism support classrooms in the School District of Philadelphia were administered the Differential Abilities Scale-2 (DAS) and Autism Diagnostic Observation Schedule (ADOS).  Parents completed the Child Symptom Inventory-4 (CSI), a standardized measure of the severity of DSM-IV psychiatric symptoms.  On average the 182 boys and 30 girls were 6.5 (SD=.9) years old, had DAS general conceptual ability scores of 60.8 (SD=20.3), and ADOS severity scores of 6.4 (SD=2.0).  The sample had the following ethnic breakdown: 46.2% black, 23.6% Caucasian, 10.4% Hispanic/Latino, 5.7% Asian, 4.2% multi-ethnic, and 9.9% unknown.  Semi-partial correlations (sr) were calculated to investigate the association between symptom severity scores and child characteristics while controlling for the other predictors. Effects sizes were interpreted based on r (small=.1, medium=.3, large=.5). 

Results: Based on the CSI, 64.6% of participants exhibited psychiatric symptoms in the severe range (t-score >70; >98^th percentile) in at least one of the following DSM-IV symptom categories: ADHD Inattentive (I), ADHD hyperactive-impulsive (HI), ADHD-combined (C), oppositional defiant disorder (ODD), conduct disorder (CD), generalized anxiety disorder (GAD), social phobia (SP), separation anxiety (SA), major depressive disorder (MDD), and dysthymic disorder.  The most common symptom category for which children demonstrated clinically significant symptoms was SP (38.7%), followed by ADHD-HI (26.4%), ADHD-C (25.8%), ADHD-I (21.7%), ODD (24.1%), MDD (10.4%), SA (9.4%), dysthymic disorder (8.5%), and CD (8.5%).  The associations between psychiatric symptom severity and other child characteristics differed for each of the symptom categories.  Higher autism symptom severity was associated with lower ODD (sr=.2), dysthymic (sr=.2), and SP (sr=.1) severity.  IQ had a negative association with ADHD-I (sr=.3). Younger age was associated with higher ADHD-I, ADHD-HI, ADHD-C and lower CD severity scores (sr =.2).  Girls had higher CD, dysthymic, SP, and SA severity scores than boys (sr=.2-.3).  Ethnicity differences in symptom severity also emerged.  Black children had lower GAD scores than Caucasian children (sr=.1).  Hispanic children had higher MDD scores than black children (sr=.2) and higher dysthymic scores than the other children. All results were significant at p < .05.

Conclusions: Clinically significant symptoms of ADHD, anxiety, disruptive behavior, and mood disorders are present in many children with ASD, and should be important considerations in treatment planning.  The associations among these symptoms and autism severity, IQ, age, gender, and ethnicity may have implications for understanding of the role of co-morbid psychiatric symptoms in ASD.