14/01/2026
The research article “ADHD as a circadian rhythm disorder: evidence and implications for chronotherapy” by Brandon Luu and Nicholas Fabiano, published in Frontiers in Psychiatry (2025), examines whether circadian rhythm dysfunction represents a core biological feature of Attention-Deficit/Hyperactivity Disorder (ADHD) rather than a secondary sleep problem. Drawing on epidemiological data, biological markers, and intervention trials, this paper synthesizes evidence showing that a large subgroup of individuals with ADHD consistently exhibit delayed circadian timing, evening chronotype, and abnormal hormonal rhythms, prompting the authors to propose circadian-informed treatment approaches.
This research demonstrates that between 73% and 80% of children and adults with ADHD experience delayed sleep–wake cycles, with objective markers such as dim-light melatonin onset delayed by about 45 minutes in children and 90 minutes in adults. The study also highlights biological mechanisms underlying this delay, including blunted and delayed cortisol rhythms, reduced pineal gland volume, and weakened expression of core clock genes (BMAL1 and PER2). Importantly, the authors review clinical trials showing that chronotherapy—particularly low-dose melatonin, morning bright light therapy, and structured behavioral sleep interventions—can successfully advance circadian phase and, in many cases, lead to improvements in ADHD symptoms, sleep quality, and daily functioning. Based on these findings, the research argues for routine screening of circadian disturbances in ADHD and supports the integration of behavioral, light-based, and melatonin-based interventions alongside standard ADHD treatments.
PMID: 41450833