Psychiatric disorders in individuals with co-occurring autism spectrum disorders (ASD) and intellectual disability (ID) are common, but diagnosis presents many challenges. The Psychopathology in Autism checklist (PAC) is among the very few instruments specifically developed for this group of individuals. The psychometric properties of the PAC…

The Aberrant Behavior Checklist (ABC) is a widely used measure in autism spectrum disorder (ASD) treatment studies. We conducted confirmatory and exploratory factor analyses of the ABC in 1,893 children evaluated as part of the Autism Treatment Network. The root mean square error of approximation was .086 for the standard item assignment, and in…

Progress in clinical research and in empirically supported interventions in the area of psychopathology in intellectual disabilities (ID) depends on high-quality assessment instruments. To this end, psychometric properties of four instruments were examined: the "Aberrant Behavior Checklist" (ABC), the "Assessment of Dual…