The literature indicates that children with Autism Spectrum Disorder (ASD) are at a heightened risk for developing anxiety disorders. Between 11% and 84% of individuals with ASD are also diagnosed with a co-occurring anxiety disorder (Muris, 1998; de Bruin et al., 2007; Green et al., 2000; Simonoff et al., 2008; Sukhodolsky et al., 2007). Despite the high frequency of co-occurrence, little research has investigated the validity of the DSM-IV Anxiety Disorder classification system in the ASD population. The present study examined 85 children, aged 7-11, with ASD and anxiety. A multitrait- (social phobia, separation anxiety disorder, and total anxiety) multimethod (self, parent, and diagnostician report) analysis was examined. Results from confirmatory factor analysis (CFA) suggest good convergent and discriminant validity for social phobia, separation anxiety disorder, and total anxiety severity. These findings provide preliminary evidence for the construct validity of the current classification system for anxiety disorders in children with ASD.

The literature indicates increased rates of anxiety disorders in children with high-functioning autism; however, little research has investigated the determinants and consequences of anxiety in autism spectrum disorder (ASD). Wood and Gadow (2010) have proposed a model in which daily stressors contribute to increased mood dysregulation and anxiety, which then exacerbates clinically impairing ASD symptoms. This study investigated the relation between diurnal cortisol levels and measures of stressors, anxiety, and ASD-symptom severity in 43 youth, aged 7-14, with high-functioning autism. Diurnal salivary cortisol samples as well as parent- and clinician- reports of stressors, anxiety and ASD-symptom severity were collected. Parent-report measures were also collected one-year later. Results from multilevel modeling suggest diurnal cortisol samples in youth with ASD follow the same daily pattern established in the typically developing population and increased daily cortisol is related to greater ASD-related daily stressors (t = 2.34, p < .05). Additionally, results from path analysis suggest anxiety partially mediates the relation between ASD-related stressors and ASD-symptom severity. Lastly, results from a multilevel analysis using longitudinal data indicate preliminary support for the mediation model. Because ASD is a prevalent, disabling condition it is of considerable importance to determine factors that are associated with greater symptom severity and functional impairment. Findings from this study establish a relation between physiological response and subjective reports of stressors and anxiety in youth with high-functioning autism and suggest that increased stressors contribute to greater anxiety and ASD symptom severity.