melatonin

Melatonin is a hormone the brain produces in response to darkness; it helps regulate the body's circadian rhythms and signals that it is time to sleep. The melatonin in dietary supplements is usually made synthetically and, in the U.S., is sold over the counter to support sleep (in some other countries it is available only by prescription).

According to NCCIH, the evidence is limited and varies by use. Research suggests melatonin may help with jet lag. For delayed sleep-wake phase disorder it appears to shorten the time to fall asleep, but NCCIH says it is uncertain whether the benefits outweigh the possible harms. For sleep problems in some children, including children with autism or ADHD, a research review found melatonin worked better than placebo for falling asleep faster and sleeping longer, though studies were relatively short and questions about long-term safety remain. NCCIH describes the evidence as stronger for reducing anxiety before surgery, while results for anxiety after surgery were mixed. For chronic insomnia, NCCIH notes there is not enough strong evidence on effectiveness or safety to recommend its use, and studies in shift workers and several other conditions have generally been small, inconclusive, or mixed.

There is no single established dose, and NCCIH does not endorse a universal dosage. The amount of melatonin in products and on labels can vary widely and may not match what the label states; studies have repeatedly found over-the-counter products (including gummies) with far more or far less melatonin than labeled. When studied, melatonin is typically taken in low doses shortly before the desired bedtime, and lower amounts taken at the right time may be preferable to higher ones. Talk to a clinician before starting melatonin, especially for a child, to decide whether it is appropriate and how to use it.

NCCIH notes that short-term melatonin use appears to be safe for most people, but information on its long-term safety is lacking. People who have epilepsy or who take blood thinners should use melatonin only under medical supervision. There is little research on melatonin's safety in pregnancy or breastfeeding, so caution is warranted, and guidelines cited by NCCIH recommend against melatonin use in people with dementia. Melatonin products marketed for children can be inaccurately labeled, and unsupervised ingestion by young children has led to thousands of emergency-room visits in recent years, so keep products out of children's reach and involve a health care provider before giving melatonin to a child.

Side effects reported in studies have generally been mild and can include headache, dizziness, nausea, and sleepiness or daytime drowsiness. In older adults, melatonin may remain active longer and cause prolonged daytime drowsiness. In children, reported effects are usually mild and can include drowsiness, headache, dizziness, agitation, and increased bedwetting or nighttime urination.

Melatonin can interact with some medications. NCCIH specifically advises that people who take blood thinners (anticoagulants) or who have epilepsy use melatonin only under medical supervision. More generally, NCCIH advises anyone taking medication to consult a health care provider before using melatonin.