Melatonin Simply Explained

1. What Is Melatonin?

Melatonin is a hormone that the body produces itself. It is made in the pineal gland in the brain and helps control the sleep-wake rhythm. The amount in the body fluctuates over the course of the day: it is higher in darkness. Melatonin also occurs in many animals and in small amounts in some plants and foods. As a preparation, it is taken when the sleep-wake rhythm is shifted in time.

2. Where Is It Found, and What Is It Made From?

Melatonin is found in small amounts in some foods. For preparations, it is mostly produced artificially. There are immediate-release and prolonged-release forms. Preparations that dissolve under the tongue have also been tested. Some preparations additionally contain other substances.

3. What Does Melatonin Do? What Research Shows

Sleep and Falling Asleep

Many studies show that melatonin can improve sleep. In various diseases, sleep quality was better under melatonin than under placebo 161823. Sleep also improved in intensive care patients 5 and in chronic muscle and bone pain 10. After operations, however, there was no difference 101415. In healthy adults with poor sleep, a prolonged-release form improved sleep efficiency and shortened sleep onset latency 39.

Children and Adolescents

In children with cerebral palsy, melatonin shortened sleep onset latency and prolonged sleep duration 28. In children with chronic sleep onset insomnia, melatonin shortened sleep onset latency and improved sleep efficiency but prolonged wake time during the night 33. In children with autism, melatonin improved sleep disorders 9. In healthy children with sleep onset problems, melatonin and light therapy shortened sleep onset latency more than psychological methods 21.

Delirium and Confusion in Hospital

In hospitalized adults, the benefit for preventing confusion states is unclear. Several studies found no difference from placebo 27293032. Some reviews reported a lower risk in intensive care patients 56, while others found no difference 18. The duration of the confusion state remained without difference in one review 6. The studies differ in form, dose, timing, and duration.

Migraine and Headache

In adults with migraine, two reviews found fewer headache days and a higher response rate under melatonin than under placebo 413. In one review, immediate-release melatonin at bedtime performed best 4. Duration and severity of attacks, painkiller consumption, and impairment also improved compared with placebo 13. As an add-on to another migraine medication, melatonin reduced the frequency and duration of attacks more than a placebo in one study 36.

Jet Lag After Flights Across Time Zones

A review found that melatonin taken shortly before bedtime at the destination reduced jet lag after flights across several time zones 26. A prolonged-release preparation had little effect. Taken at the wrong time of day, melatonin can delay adaptation 26. The strength of evidence is low because the finding is based on reviews and dose, timing of intake and duration are not uniform.

Shift and Night Work

In overweight nurses working night shifts who took melatonin on their nights off, the shift of the internal rhythm was reduced more than under placebo 46. Weight and waist circumference decreased only in early chronotypes with strong rhythm shift 46. A second analysis of the same study found no difference in energy intake and meal times 45. The evidence is weak because both analyses are based on the same small study.

Shifted Sleep-Wake Rhythm

In adults with ADHD and delayed sleep-wake rhythm, low-dose melatonin advanced the evening melatonin onset 42. However, sleep times did not shift accordingly in an analysis of the same study 43. Reviews describe better alignment of the internal rhythm through melatonin 47. In Alzheimer's dementia, regulation remains unclear 48. The evidence is weak because only one controlled trial (with a comparison group) is available.

Other Investigations

Melatonin improved quality of life in heart failure and in breast cancer under antihormone therapy 3135. A review also found this in Alzheimer's dementia 24. Anxiety and depression scores improved under melatonin, including in Parkinson's, women with the hormonal condition PCOS, and people in methadone treatment 384041. Several studies found improvements in blood sugar and inflammation markers as well as oxidative stress 121720. Studies found no difference from placebo for fatigue during breast cancer radiation, brain damage markers after brain injury, and vascular function in healthy individuals 343744.

4. How Was Melatonin Taken in the Studies?

In the studies, melatonin was mostly taken as a tablet or capsule. Sometimes they were prolonged-release or sublingual preparations. Many studies do not state the release type. Some studies tested melatonin together with other substances, such as zinc and multivitamins. Such results apply to the mixture, not to melatonin alone. Form, dose, timing, and duration differ between the studies.

5. Is Melatonin Safe? Side Effects in the Studies

Melatonin can cause drowsiness, especially in the morning. In one review, melatonin caused drowsiness less often than the migraine medication amitriptyline 13. In children with autism, morning drowsiness was reported as a side effect under melatonin 9. A review on high doses mentions reduced insulin release, suppression of ovulation, and reduced attention 22. In intensive care patients, no more adverse events occurred 5. Individual case reports suggest risks in epilepsy and when taking the blood thinner warfarin 26.

All details with tables and sources: full expert page on Melatonin