A Distinct Three-Factor Structure of Restricted and Repetitive Behaviors in an Epidemiologically Sound Sample of Preschool-Age Children with Autism Spectrum Disorder

Prior studies investigating restricted and repetitive behavior (RRB) subtypes within autism spectrum disorder (ASD) have found varied factor structures for symptom groupings, in part, due to variation in symptom measurement and broad sample age ranges. This study examined RRBs among 827 preschool-age children, ages 35 to 71 months, through an exploratory factor analysis of RRB items from the Autism Diagnostic Interview-Revised (ADI-R) collected through the Study to Explore Early Development. The factor structures of RRBs among children with confirmed ASD versus those with non-autism developmental concerns were qualitatively compared. Correlations between RRB factors and participant characteristics were examined in the ASD group. Three conceptually well-defined factors characterized as repetitive sensorimotor behaviors (RSMB), insistence on sameness (IS), and a novel stereotyped speech (SPEECH) factor emerged for the ASD group only. Distinct factors were supported by different clinical correlates. Findings have implications for improving differential diagnosis and understanding of ASD symptomatology in this age range

Phenomenology and measurement of circumscribed interests in autism spectrum disorders

Circumscribed interests (CI) are important and understudied symptoms that affect individuals with autism spectrum disorders (ASD). The present study sought to develop quantitative measures of the content, intensity and functional impairment of CI in 50 children with high-functioning ASD compared to an age-, IQ-, and gender-matched sample of 50 typically developing (TD) peers. The Interests Scale, a parent-rating questionnaire, and the Interview for Repetitive Behaviors, a semi-structured interview, were used to assess CI. Groups did not differ on the number of interests children held, but they did differ on types of interests and impairment associated with them. The interests of ASD participants were more likely to be nonsocial in nature (e.g. mechanical systems) than TD participants. Parents of children with ASD endorsed higher degrees of functional impairment on metrics including frequency, interference, resistance when interrupted, flexibility, and accommodation required, as well as less involvement of other people, than parents of children with TD. These findings suggest that interests of individuals with ASD differ qualitatively and in intensity from individuals with TD. The present study offers further support for the notion that CI reflect a clinically significant feature of ASD that warrants intervention in some children