Subdomains of restricted and repetitive behaviors within autism: Exploratory structural equation modeling using the diagnostic interview for social and communication disorders.

The current study aimed to explore the factor structure of a broad range of restricted and repetitive behaviors (RRB) within the autism spectrum. Exploratory structural equation modeling was conducted using individual item-level data from the Diagnostic Interview for Social and Communication Disorders (DISCO). DISCO is a comprehensive semi-structured interview used by clinicians to elicit information from caregivers about the individual's profile of development and behavior. Data from a sample of 226 individuals with a clinical diagnosis of autism spectrum disorder (ASD) (189 males; M age  = 11.82 years, SD age  = 7.87) were analyzed. The six-factor structure provided the most optimal and interpretable fit (comparative fit index = 0.944, Tucker-Lewis index = 0.923, root mean square error of approximation = 0.018). Derived factors were interpreted as repetitive motor behaviors (RMB), unusual sensory and object focused interests (USOI), sensory sensitivity (SS), insistence on sameness (IS), circumscribed interests (CI) and stereotyped language (SL). Age was significantly negatively associated with RMB, USOI and SL but not with SS, IS or CI factor scores. None of the factors were associated with sex. ASD individuals with intellectual disability (ID) had the highest RMB, USOI, SS and SL scores while those without ID had the highest IS and CI scores. Our findings provide preliminary evidence for the utility of the DISCO as a comprehensive measure of several distinct RRB domains in both research and clinical contexts. Importantly, the current investigation highlights crucial areas for measurement development. LAY SUMMARY: The diagnostic Interview for Social and Communication Disorders (DISCO) is a detailed caregiver report clinical interview designed to capture a wide range of key features associated with autism spectrum disorder, including restricted and repetitive behaviors (RRB). This paper provides initial evidence that the DISCO is a promising measure for assessing a wide range of RRB including repetitive motor behaviors, insistence on sameness, circumscribed interests, unusual interests in sensory stimuli, sensory sensitivity and stereotypic language.