The sleep-circadian connection: pathways to understanding and supporting autistic children and adolescents and those...

Autism and attention-deficit hyperactivity disorder (ADHD) are among the most common neurodivergent neurotypes worldwide. Epidemiological evidence shows that sleep and circadian disturbances, such as difficulty initiating and maintaining sleep, and delayed sleep-wake phase, are highly prevalent in autistic children, children with ADHD, and those with both neurotypes. Despite scientific advancements, a comprehensive framework integrating sleep and circadian mechanisms with targeted interventions for autism and ADHD remains underdeveloped. In this Review we examine sleep and circadian rhythm differences in autistic children and adolescents, and in those with ADHD or both neurotypes, focusing on the underlying biological mechanisms. We discuss recent advances in the genetic and molecular links between sleep, circadian rhythms, and neuroplasticity, alongside the influence of these systems on physiology and therapeutic strategies. Both pharmacological and non-pharmacological interventions are considered, with an emphasis on the need for an integrated support model that accounts for the dynamic interplay between sleep and circadian rhythms in these populations. We identify key gaps in the current evidence base, particularly in relation to non-pharmacological interventions, and outline future research directions. Although most randomised controlled trials in children and adolescents have focused on behavioural sleep interventions, we also discuss emerging findings from trials using alternative approaches, such as targeted light therapy in adults, with implications for paediatric populations. Finally, we emphasise the importance of incorporating the perspectives of autistic children and adolescents and those with ADHD, as well as their parents and caregivers, into research designs.