Circadian disruption in ADHD: Is the gut microbiome the missing link?

Sleep disturbances are common in children with attention deficit hyperactivity disorder (ADHD), yet they are often viewed as secondary rather than clinically meaningful contributors to symptom variability. At the same time, growing interest in the gut–brain axis has highlighted the role of the gastrointestinal microbiome in neurodevelopment, neurotransmitter signaling, and immune regulation. However, the potential link between gut microbiota and circadian disruption in ADHD remains underexplored. In this commentary, we propose that the gut microbiome may act as an upstream regulator of circadian rhythm in ADHD. Microbial metabolites, including short chain fatty acids and tryptophan derivatives, can influence host clock systems, modulate melatonin pathways, and affect sleep timing and stability. Disruption of microbial composition may therefore contribute to circadian misalignment, which in turn shapes attention, emotional regulation, and behavioral control. In this framework, sleep disturbance is not simply a coexisting feature, but a potential mediator of clinical expression. Recognizing a gut–circadian–sleep axis in ADHD may offer a more integrated approach to patient assessment and management. While current evidence remains largely associative, this perspective highlights the need for longitudinal and interventional studies that consider microbiome, circadian rhythm, and behavior together.