Anxiety Disorders Interview Schedule-Autism Addendum: Reliability and Validity in Children With Autism Spectrum Disorder.

Assessing anxiety in autism spectrum disorder (ASD) is inherently challenging due to overlapping (e.g., social avoidance) and ambiguous symptoms (e.g., fears of change). An ASD addendum to the Anxiety Disorders Interview Schedule-Child/Parent, Parent Version (ADIS/ASA) was developed to provide a systematic approach for differentiating traditional anxiety disorders from symptoms of ASD and more ambiguous, ASD-related anxiety symptoms. Interrater reliability and convergent and discriminant validity were examined in a sample of 69 youth with ASD (8-13 years, 75% male, IQ = 68-143) seeking treatment for anxiety. The parents of participants completed the ADIS/ASA and a battery of behavioral measures. A second rater independently observed and scored recordings of the original interviews. Findings suggest reliable measurement of comorbid (intraclass correlation = 0.85-0.98, κ = 0.67-0.91) as well as ambiguous anxiety-like symptoms (intraclass correlation = 0.87-95, κ = 0.77-0.90) in children with ASD. Convergent and discriminant validity were supported for the traditional anxiety symptoms on the ADIS/ASA, whereas convergent and discriminant validity were partially supported for the ambiguous anxiety-like symptoms. Results provide evidence for the reliability and validity of the ADIS/ASA as a measure of traditional anxiety categories in youth with ASD, with partial support for the validity of the ambiguous anxiety-like categories. Unlike other measures, the ADIS/ASA differentiates comorbid anxiety disorders from overlapping and ambiguous anxiety-like symptoms in ASD, allowing for more precise measurement and clinical conceptualization. Ambiguous anxiety-like symptoms appear phenomenologically distinct from comorbid anxiety disorders and may reflect either symptoms of ASD or a novel variant of anxiety in ASD.