BACKGROUND: Sleep disturbances are common in individuals with autism spectrum disorder (ASD) or bipolar disorder (BD). However, to the best of our knowledge, there has been no study investigating prevalence and features of sleep disorders in youth with ASD with and without comorbid BD. The aim of this case-controlled study was to investigate sleep disturbances in autistic youth with and without comorbid BD. METHODS: The study included 43 individuals with both ASD and BD as the case group, and 43 age and gender-matched participants with ASD but no mood disorders as the control group. Both groups were assessed using the Sleep Disturbance Scale for Children (SDSC), the Childhood Autism Rating Scale (CARS), and the Aberrant Behavior Checklist (ABC). RESULTS: The case group exhibited significantly higher levels of sleep breathing disorders, disorders of arousal, disorders of excessive somnolence, and sleep hyperhidrosis on the SDSC compared to the control group (p <
0.05). Partial correlation analysis revealed a significant association between total SDSC scores and total ABC scores in the case and control groups (r = 0.424, p = 0.005
r = 0.629, p <
0.001, respectively) CONCLUSIONS: Sleep disturbances are common in youth with ASD with further increased rates in the presence of comorbid BD. Sleep disturbances are also associated with more behavioral problems among youth with ASD regardless of comorbid BD diagnosis. Clinicians working with youth with ASD should routinely assess sleep habits and related problems and should give particular attention in the presence of comorbid mood disorders. This study highlights the importance of recognizing and managing sleep disturbances in this unique population.