Effortful Control but Not Negative Affectivity Predicts Intensity of Restricted Repetitive Behaviors in Toddlers With Neurodevelopmental Conditions

Objective Restricted repetitive behaviors (RRBs) are prevalent across neurodevelopmental conditions. It has been hypothesized that greater RRB severity reflects elevated distress or diminished regulatory capacity. To test these hypotheses, we examined prospective associations between early negative affectivity (NA) and effortful control (EC) and later RRB severity in a transdiagnostic sample of toddlers with and without autism. Method Participants were 238 toddlers with neurodevelopmental conditions (autism n =165; non-autism n =73). NA and EC were assessed at Time 1 (M age =24.4 months, SD=5.2) using the Toddler Behavior Assessment Questionnaire or the Early Childhood Behavior Questionnaire. At Time 2 (M age =42.2 months, SD=7.3), RRB severity was assessed using the Autism Diagnostic Observation Schedule (ADOS) and the Autism Diagnostic Interview–Revised (ADI-R). Multivariate regression models tested whether Time 1 NA and EC predicted Time 2 RRBs, controlling for age, sex, nonverbal developmental quotient, Time 1 RRBs, and visit year. Results Higher EC at Time 1 predicted lower ADI-R RRB scores at Time 2 ( p