Prevalence of Anxiety and Associated Psychiatric Comorbidities Among Children with Autism Spectrum Disorder: An Autism Treatment Network Study

Background:   Anxiety disorders and symptoms are highly prevalent in autism spectrum disorders (ASD), although estimates vary widely from 11% to 84% depending on the study methods (see review by White et al., 2009).  Moreover, few, if any, studies have examined anxiety across development. There are also scant data on the psychiatric comorbidities associated with anxiety in ASD. A greater understanding of the prevalence and risk factors of anxiety in ASD is therefore critical for developing targeted treatments that can reduce the burden of suffering for children and their families.

Objectives: a) To observe the prevalence of parent-reported anxiety symptoms among youth with an ASD across development, and b) to examine what psychiatric comorbidities, if any, are associated with increased anxiety symptoms.

Methods: Data from 1,316 children were obtained from the Autism Treatment Network (ATN) registry, a multi-site collaboration among 14 leading autism centers in the US and Canada that focuses on addressing the medical needs of children with ASD. The ATN enrolls children, ages 2 to 17.9 years, with a diagnosis of ASD as confirmed by the Autism Diagnostic Observation Schedule (ADOS; Lord et al, 2002) and DSM-IV-TR criteria. Children also undergo standardized cognitive testing. Upon enrollment, parents complete many questionnaires including the Child Behavior Checklist (CBCL; Achenbach and Rescorla, 2001), an established measure of psychopathology in youth. The CBCL Anxiety Problems scale was used to categorize children into three groups: little or no anxiety (T score < 65), subclinical anxiety (T-score of 65-69), and clinical anxiety (T-score > 69). Multivariate analyses were performed to examine the psychiatric comorbidities, as measured by the CBCL, and demographic characteristics associated with increased anxiety. Analyses were conducted separately for children < 6 years and 6-18 years given the different CBCL modules for each age group.

 Results: For children < 6 years (n = 716), 19% of children had clinical anxiety, and 6% had sub-clinical anxiety. No differences in age, race, parental education, or IQ emerged among the three anxiety groups. Results from the multiple linear model indicated that increased PDD, Affective, ADHD, and ODD problems were strongly associated with increased anxiety (all p < .001).  For children 6-18 years (n = 600), 30% and 22.5% had clinical and subclinical anxiety, respectively. In this group, increased anxiety was associated with older age and Caucasian ethnicity (all p < .05), although these variables were not significant in the multivariate analysis. Similar to the younger children, increases in all comorbidities (Affective, Somatic, ODD, ADHD, and Conduct problems) were associated with increases in anxiety (all p < .001).

 Conclusions: The prevalence of parent-reported anxiety in children with ASD is high, with nearly 20% of young children and over 50% of older children experiencing clinical or subclinical anxiety. In each age group, anxiety was significantly associated with multiple psychiatric comorbidities. These data indicate the need for comprehensive care of children with ASD and anxiety. Further research is needed to determine whether anxiety and associated psychiatric comorbidities represent distinct clinical entities or one complex clinical syndrome.