This randomized trial studied 51 adults aged 18 to 55 at an adult ADHD clinic in The Netherlands. All had both ADHD and delayed sleep phase syndrome, a pattern where the body clock runs late. They were not taking ADHD medication and had relatively little other psychiatric illness. Each person got placebo, melatonin, or melatonin plus morning bright light for 3 weeks. In the trial, melatonin was given at a low dose (0.5 mg/d), timed to each person.
The team tracked the evening rise of melatonin in the body, a marker of body clock timing. These results come from the 36 people whose rise came late. In that group, melatonin moved it earlier compared with placebo (1 h 28 min). Adding bright light moved it earlier still (1 h 58 min). The two active groups did not clearly differ from each other.
Melatonin alone also lowered self-reported ADHD symptoms by a modest amount (12%) when all participants were included. Melatonin plus bright light did not change symptoms. The shift in body clock did not explain the symptom change. Once treatment had stopped for two weeks, both measures were back where they began. No adverse events occurred.
The sample was small, and symptoms were self-reported rather than measured objectively. In the late-rise group alone, the symptom drop (14%) did not reach statistical significance.
The authors suggest timed low-dose melatonin could be an added treatment for a delayed body clock in adults with both conditions, and that treatment should last longer. Anyone curious about melatonin should talk to a clinician about their situation.
Source: van Andel E, Bijlenga D, Vogel S, et al.. Effects of chronotherapy on circadian rhythm and ADHD symptoms in adults with attention-deficit/hyperactivity disorder and delayed sleep phase syndrome: a randomized clinical trial. Chronobiology International (2020). doi:10.1080/07420528.2020.1835943