In a preliminary trial, supplementation with melatonin (3 mg per day at bedtime for at least three months) resulted in an improvement in the abnormalities observed on eye examination in the majority of cases.⁸ Melatonin is believed to work by regulating eye pigmentation (and, consequently, the amount of light reaching the retina) and by functioning as an antioxidant.

Melatonin is a hormone secreted by the pineal gland in the brain. It is partially responsible for regulating sleep-wake cycles. Cognitive function is linked to adequate sleep and normal sleep-wake cycles. Cognitive benefits from melatonin supplementation have been suggested by preliminary research in a variety of situations and may derive from the ability of melatonin to prevent sleep disruptions.^9,10,11,12 A double-blind trial of ten elderly patients with mild cognitive impairment showed that 6 mg of melatonin taken two hours before bedtime significantly improved sleep, mood, and memory, including the ability to remember previously learned items.¹³ However, in a double-blind case study of one healthy person, 1.6 mg of melatonin had no immediate effect on cognitive performance.¹⁴

The long-term effects of regularly taking melatonin supplements remain unknown, and many healthcare practitioners recommend that people take no more than 3 mg per evening. A doctor familiar with the use of melatonin should supervise people who wish to take it regularly.

In a double-blind trial, supplementation with prolonged-release melatonin (2 mg each night for 24 weeks) significantly improved cognitive function and sleep quality, compared with a placebo, in patients with Alzheimer's disease.¹⁵ The beneficial effect of melatonin was more pronounced in patients who were suffering from insomnia than in those who were not, suggesting that poor sleep quality contributes to impaired cognitive function in people with Alzheimer's disease.

The function of the pineal gland and its cyclic secretion of melatonin may be disturbed in people with migraine headaches.¹⁶ Preliminary evidence suggests that 5 mg per day of melatonin, taken 30 minutes before bedtime, may reduce symptoms of migraine headache.¹⁷ A double-blind trial found that taking 3 mg of melatonin at bedtime each day for 12 weeks significantly decreased the frequency of migraines in people suffering from recurrent migraines.¹⁸ Another double-blind trial found that taking 2 mg of melatonin 1 hour before bedtime each day for 8 weeks was not more effective than a placebo for decreasing migraine frequency.¹⁹

In the positive study described above, the reduction in migraine frequency was assessed only in the third month of treatment. It is possible that it takes a few months for melatonin to start working. The negative results in the other study cited above could have been due either to the shorter duration of treatment or to the lower amount of melatonin given.

Researchers have found low levels of the hormone melatonin in cluster headache patients.^20,21,22,23 In a small double-blind trial, a group of cluster headache sufferers took a 10 mg evening dose of melatonin for 14 days. About half of the group saw a significant decrease in the frequency of their headaches within three to five days, after which no further headaches occurred until melatonin was discontinued.²⁴ Melatonin appears to be effective against both types of cluster headache (e.g., episodic and chronic). ²⁵ More research is needed to establish the long-term effects of melatonin supplementation on cluster headache.

Melatonin supplementation may be useful in the treatment of fibromyalgia. In a preliminary trial, 3 mg of melatonin at bedtime was found to reduce tender points and to improve sleep and other measures of disease severity, though pain and fatigue improved only slightly.²⁶

Caution: Melatonin is a potent hormone and its long-term safety is not established. Melatonin should only be taken with medical supervision.

Melatonin is a natural hormone that regulates the human biological clock. The body produces less melatonin with advancing age, which may explain why elderly people often have difficulty sleeping²⁷ and why melatonin supplements improve sleep in the elderly.²⁸

Middle-aged adults (average age, 54 years) with insomnia also have lower melatonin levels, compared with people of the same age without insomnia.²⁹ However, there is not much research on the use of melatonin for sleep problems in middle-aged people.

Double-blind trials have shown that melatonin facilitates sleep in young adults without insomnia,³⁰ but not in young people who suffer from insomnia.³¹However, one trial found that children with sleep disturbances stemming from school phobia had improved sleep after taking 1 mg of melatonin per night for one week, then 5 mg per night for one week, then 10 mg per night for a third week.³²

The results of one double-blind trial also indicate that a controlled release melatonin supplement providing 2 mg per day improves sleep quality in people with schizophrenia.³³

Normally, the body makes melatonin for several hours per night—an effect best duplicated with controlled-release supplements. Trials using timed-release melatonin for insomnia have reported good results.³⁴ Many doctors suggest taking 0.5 to 3 mg of melatonin one and a half to two hours before bedtime. However, because melatonin is a potent hormone, the long-term effects of which are unknown, it should be taken only with the supervision of a doctor.

Melatonin is a natural hormone that regulates the human biological clock and may be helpful in relieving symptoms of jet lag, according to some,^35,36 though not all,^37,38 double-blind studies. One double-blind trial, involving international flight crew members, found that melatonin supplementation was helpful when started after arriving at the destination but not when started three days before leaving.³⁹ Another double-blind study compared various amounts and forms of melatonin taken at bedtime for four days after the flight by people who traveled through six to eight time zones.⁴⁰ Fast-release melatonin supplements were found to be more effective than the controlled-release supplements. A 5 mg and 0.5 mg fast-release melatonin were almost equally effective for improving sleep quality, time it took to fall asleep, and daytime sleepiness.

Caution: Melatonin is a potent hormone and its long-term safety is not established. Melatonin should only be taken with medical supervision.

In a double-blind trial, melatonin supplementation (3 mg taken nightly) improved symptoms of tinnitus.⁴¹ Although improvement did not reach statistical significance for all participants, the results were significant in those who reported more severe symptoms (such as two-sided vs. one-sided tinnitus). Among participants who had difficulty sleeping due to tinnitus, 47% of those who took melatonin reported sleep improvement after one month, compared with only 20% of those who took the placebo. Similar improvements in tinnitus were reported in a preliminary trial that used 3 mg of melatonin each night for four weeks.⁴²

Antioxidants have been studied as topical agents for protection against sunburn. Animal studies have found sunscreen-like effects from topical application of a vitamin C and vitamin E combination, and a controlled human study reported ultraviolet protection from the use of a lotion containing 0.02% to 0.05% of the selenium-containing amino acid known as selenomethionine.^43,44 The topical use of the hormone melatonin has been shown to protect human skin against ultraviolet rays in double-blind research.^45,46 A double-blind human trial tested topical vitamins C and E and melatonin, alone and in combinations, and found the highest degrees of protection from combination formulations containing 2% vitamin E, 5% vitamin C, and 1% to 2.5% melatonin.⁴⁷ Other studies in which topical antioxidants were applied after ultraviolet exposure have found no benefits.^48,49

Melatonin might help some people suffering from depression. Preliminary double-blind research suggests that supplementation with small amounts of melatonin (0.125 mg taken twice per day) may reduce winter depression.⁵⁰ People with major depressive disorders sometimes have sleep disturbances. A timed-release preparation of melatonin (5–10 mg per day for four weeks) was shown to be effective at improving the quality of sleep in people with major depression who were taking fluoxetine (Prozac), but melatonin did not enhance its antidepressant effect.⁵¹ There is a possibility that melatonin could exacerbate depression, so it should only be used for this purpose under a doctor’s supervision.

The results of one double-blind trial indicate that melatonin supplementation improves sleep quality in people with schizophrenia.⁵² In one study, all patients with a diagnosis of schizophrenia were found to have low melatonin output. Replacement of melatonin with 2 mg of a controlled-release supplement per day for three weeks improved sleep duration and quality compared to placebo. When patients receiving placebo were crossed over to the melatonin group, they too experienced improved sleep quality.

In a preliminary trial, supplementation with melatonin (3 mg per day at bedtime for at least three months) resulted in an improvement in the abnormalities observed on eye examination in the majority of cases.⁵³ Melatonin is believed to work by regulating eye pigmentation (and, consequently, the amount of light reaching the retina) and by functioning as an antioxidant.

Supplementing with 0.5 mg of melatonin lowered intraocular pressure of healthy people,⁵⁴ but there have been no studies on the effects of melatonin in people with glaucoma.

Melatonin plays a role in the regulation of gastrointestinal function and sensation. In a double-blind trial, people with irritable bowel syndrome and associated sleep disturbances received 3 mg of melatonin or a placebo at bedtime for two weeks. Compared with the placebo, melatonin significantly decreased the severity of abdominal pain, although it did not affect bloating, stool frequency, or sleep patterns.⁵⁵ Melatonin was also effective in another double-blind trial.⁵⁶

Melatonin is a hormone secreted by the pineal gland in the brain. It is partially responsible for regulating sleep-wake cycles. Cognitive function is linked to adequate sleep and normal sleep-wake cycles. Cognitive benefits from melatonin supplementation have been suggested by preliminary research in a variety of situations and may derive from the ability of melatonin to prevent sleep disruptions.^58,59,60,61 A double-blind trial of ten elderly patients with mild cognitive impairment showed that 6 mg of melatonin taken two hours before bedtime significantly improved sleep, mood, and memory, including the ability to remember previously learned items.⁶² However, in a double-blind case study of one healthy person, 1.6 mg of melatonin had no immediate effect on cognitive performance.⁶³

The long-term effects of regularly taking melatonin supplements remain unknown, and many healthcare practitioners recommend that people take no more than 3 mg per evening. A doctor familiar with the use of melatonin should supervise people who wish to take it regularly.

Caution: Melatonin is a potent hormone and its long-term safety is not established. Melatonin should only be taken with medical supervision.

In a double-blind trial, melatonin supplementation (3 mg taken nightly) improved the symptoms of tinnitus.⁶⁴ Although improvement did not reach statistical significance for all participants, the results were significant in those who reported more severe symptoms (such as two-sided vs. one-sided tinnitus). Among participants who had difficulty sleeping due to tinnitus, 47% of those who took melatonin reported sleep improvement after one month, compared with only 20% of those who took placebo. Similar improvements in tinnitus were reported in a preliminary trial that used 3 mg of melatonin each night for four weeks.⁶⁵