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Background:
Melatonin is a hormone produced by the pineal gland, located in the middle of the brain; it regulates the sleep-wake cycle. Melatonin used in supplements is derived from animals or produced artificially.
Medicinal Claims:
Melatonin is used to treat insomnia and to help minimize the effects of jet lag. People who are traveling across time zones may benefit from melatonin given on the day or night of departure and for 2 or 3 nights after arrival. Melatonin has been used to prevent pregnancy, to enhance the immune system, and to prevent cancer.
Evidence suggests that melatonin supplements can affect the sleep-wake cycle. However, in one large well-designed study, melatonin supplements did not relieve symptoms of jet lag, and only a few small studies suggest that these supplements can treat insomnia. There is no evidence that melatonin can prevent pregnancy or cancer.
Possible Side Effects:
Drowsiness may occur 30 minutes after taking melatonin and lasts for about 1 hour. Whether melatonin is safe when used long-term is unknown. Theoretically, a viral or prion infection (see Travel and Health: Sleep Disturbance) could result from taking melatonin derived from animal brains but not from taking artificially produced melatonin. Headache and transient depression have been reported. In people who are depressed, melatonin may worsen symptoms. Melatonin is best taken under medical supervision.
Last full review/revision February 2003
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