Melatonin

Melatonin is a hormone that regulates the sleep–wake cycle. It is primarily released by the pineal gland. As a supplement, it is often used for the short-term treatment of trouble sleeping such as from jet lag or shift work. Evidence of benefit, however, is unclear. One review found onset of sleep occurred 6 minutes faster with use but found no change in total time asleep. It may work as well as the medication ramelteon. It is typically taken by mouth. Side effects from supplements are minimal at low doses for short durations. Side effects may include sleepiness, headaches, nausea, diarrhea, and abnormal dreams. Use is not recommended during pregnancy or breastfeeding. Use is also not recommended in those with liver problems. In animals (including humans), melatonin is involved in synchronizing the circadian rhythm including sleep–wake timing, blood pressure regulation, and seasonal reproduction. Many of its effects are through activation of the melatonin receptors, while others are due to its role as an antioxidant. In plants it functions to defend against oxidative stress. Melatonin is also present in various foods. Melatonin was discovered in 1958. It is sold over the counter in Canada and the United States. In the United Kingdom it is a prescription-only medication. A month's supply costs about US $1 to 4 in the United States. In the United Kingdom a month's supply costs the NHS about 15 pounds. It is not FDA-approved for any use. In Australia and Europe, it is approved for trouble sleeping in people over the age of 54. Positions on the benefits of melatonin for insomnia are mixed. An Agency for Healthcare Research and Quality (AHRQ) review from 2015 stated that evidence of benefit in the general population was unclear. A review from 2017 found a modest effect on time until onset of sleep. Another review from 2017 put this decrease at 6 minutes to sleep onset but found no difference in total sleep time. Melatonin may also be useful in delayed sleep phase syndrome. Melatonin appears to work as well as ramelteon but costs less. Melatonin is a safer alternative than clonazepam in the treatment of REM sleep behavior disorder – a condition associated with the synucleinopathies like Parkinson's disease and dementia with Lewy bodies. In Europe it is used for short-term treatment of insomnia in people who are 55 years old or older. It is deemed to be a first line agent in this group. Melatonin reduces the time until onset of sleep and increases sleep duration in children with neurodevelopmental disorders. A 2016 review found no evidence that melatonin helped sleep problems in people with moderate to severe dementia due to Alzheimer's disease.