[Sleep and neurodevelopment: a timely subject]

Neurodevelopmental disorders (NDDs) include a heterogeneous group of conditions characterized by an alteration of neurodevelopmental processes leading to a significant impact on the individual's personal, social, and/or academic functioning. Among the many comorbidities frequently associated with NDDs, sleep disturbances play a major role, affecting between 30% and 80% of concerned people. This article explores the various links between sleep and NDDs through a review of the scientific literature highlighting the most recent research in this area, with a particular focus on two neurodevelopmental disorders: autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD). Sleep is an essential physiological process regulated by homeostatic and circadian mechanisms, playing a crucial role in brain maturation. In children with ASD, a decrease in the activity of enzymes responsible for melatonin synthesis has been identified, leading to a melatonin production and secretion deficiency that is associated with sleep-wake cycle disturbances. As a result, autistic people suffer from sleep-onset insomnia, sleep-maintenance insomnia with particularly long nocturnal awakenings, and reduced total sleep duration. In ADHD, on the other hand, the most commonly observed sleep disorders include delayed sleep phase syndrome and restless legs syndrome, both responsible for sleep-onset insomnia. Due to its essential role in memory consolidation, emotional regulation, and attention, sleep directly influences an individual's cognitive and behavioral development. Thus, sleep disorders in children with ADHD exacerbate inattention, hyperactivity and impulsivity, while in children with ASD, they amplify emotional regulation difficulties and behavioral disturbances. Identifying sleep disorders for their management in patients with NDDs is essential to improving their quality of life and reducing the severity of their daytime symptoms. Therapeutic interventions, whether behavioral or pharmacological - particularly melatonin administration - have shown significant efficacy. An integrated, multidisciplinary approach can optimize patient care and enhance their social and cognitive adaptation. A better understanding of the interactions between sleep disorders and NDDs thus opens new avenues for improving strategies in the management of individuals with NDDs.