Interactions of Sleep and Repetitive Behavior in Attention-Deficit/Hyperactivity Disorder, Autism, and Intellectual Disability

Objective: Sleep problems and restricted and repetitive behaviors (RRBs) feature in neurodevelopmental conditions such as autism, attention-deficit/hyperactivity disorder (ADHD), and intellectual disabilities (ID). It is unclear whether their interaction differs between conditions, and whether symptom dimensions might capture differences better than diagnostic categories. Method: In a preregistered cross-sectional analysis of the Healthy Brain Network community sample enriched for neurodevelopmental conditions (n = 2,394, 5-21 years), linear regression modeled parent-reported sleep disturbance and RRBs by diagnostic category and symptom dimensions (autistic traits, ADHD traits, IQ). Results: All symptom dimensions predicted sleep disturbance (p < .001), whereas only ADHD consistently predicted greater sleep disturbance (d = .35, 95% CI [.24, .47]) among diagnostic categories relative to typical development. All diagnostic categories and symptom dimensions were associated with RRB severity. Sleep disturbance and RRBs were associated in the entire sample (beta = .30, p < .001). Sleep disturbance predicted RRBs at all levels of autistic and ADHD traits, but most strongly with high autistic and low ADHD traits (beta = .16) and least strongly when both were high (beta = .13). Dimensional measures explained more variance than diagnoses for sleep disturbance (R square = .14 vs .03) and RRBs (R square = .38 vs .21), and provided better model fits in all comparisons. Conclusion: Autistic and ADHD traits shaped the relationship between sleep disturbance and RRBs, whereas diagnoses did not. Neurodevelopmental symptom assessments might be more informative than diagnoses to manage sleep and RRBs, though the cross-sectional design and parent report limit inference.