Abstract
Given the prominence of the Aberrant Behavior Checklist (ABC), Irritability Subscale (ABC-I), in treatment outcome studies, we conducted a critical examination of its internal consistency and relationship to other measures of irritability in 758 psychiatrically hospitalized youth with autism spectrum disorder. In exploratory and confirmation samples, we conducted factor and bifactor analyses to describe the internal structure of the ABC-I. Our results suggest that the ABC-I roughly represents a unidimensional construct of irritability, as indicated by a general factor in bifactor analysis. In addition to irritability, subordinate factors are presented that represent tantrums, verbal outbursts, self-harm, and negative affect. Notably, self-harm items explain a large proportion of variance independent of irritability. Therefore, their contribution in analyses of treatment effects should be considered. Further study or revision of the ABC-I may improve convergent validity with transdiagnostic formulations of irritability as well as prevent confound from self-harm in treatment studies for irritability in ASD.