Attention‑Deficit/Hyperactivity Disorder (ADHD) is increasingly recognized as having a strong circadian component, according to a 2025 perspective article in Frontiers in Psychiatry. The article reports that sleep disturbances affect up to 80 % of adults with ADHD and up to 82 % of children, while delayed sleep‑wake timing occurs in as many as 78 % of individuals. Biological markers show a consistent phase delay: dim‑light melatonin onset (DLMO) is shifted later by about 45 minutes in children and approximately 90 minutes in adults with ADHD compared with neurotypical peers.
These melatonin delays are accompanied by blunted and delayed cortisol rhythms, reduced pineal gland volume, and attenuated expression of core clock genes such as BMAL1 and PER2. The article notes that lower peripheral clock‑gene rhythmicity correlates with ADHD symptom severity, suggesting a molecular link between circadian disruption and the disorder.
Intervention studies described in the paper demonstrate that the circadian phase can be advanced in ADHD populations. In a randomized trial of adults, 0.5 mg of melatonin taken nightly advanced DLMO by 88 minutes and was associated with a 14 % reduction in ADHD symptoms. A separate placebo‑controlled trial of 101 medication‑free children with chronic sleep‑onset insomnia used 3–6 mg of melatonin nightly for four weeks; DLMO advanced by 44 minutes in the treatment group while the control group showed a 13‑minute delay, and total sleep time increased by 20 minutes versus a loss of 14 minutes in controls. Long‑term follow‑up indicated that 65 % of children continued melatonin use, and discontinuation resulted in a phase delay of sleep in 92 % of participants, with reported improvements in behavior (71 %) and mood (61 %).
Bright‑light therapy also shows promise. The article cites experiments in healthy adults where a week of natural light‑dark cycles shifted DLMO approximately 2.6 hours earlier, and it suggests that similar morning light exposure could benefit those with ADHD. Based on these findings, the authors propose a pragmatic, behavioral‑first pathway: routine screening for sleep and circadian disturbances, characterization through chronotype questionnaires, sleep tracking, and DLMO measurement when feasible, followed by fixed wake times, morning bright‑light exposure, evening light restriction with screen hygiene, regularized zeitgebers, and, when appropriate, low‑dose melatonin for confirmed or probable DLMO delays.