Melatonin, a hormone produced by the pineal gland (located in the middle of the brain), regulates the sleep-wake cycle. Melatonin used in supplements is derived from animals or produced artificially. In some countries, melatonin is considered a drug and is regulated as such.
People use melatonin mostly to treat insomnia and to help minimize the effects of jet lag or of shift work. People who are traveling across time zones may take melatonin on the day or night of departure and for 2 or 3 nights after arrival. People who rotate work shifts may take melatonin before going to bed.
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.
Drowsiness may occur 30 minutes after taking melatonin and lasts for about 1 hour. Otherwise, melatonin seems to have few short-term side effects, although headache and temporary depression have been reported. Whether melatonin is safe when used long-term is unknown. Theoretically, a viral or prion infection (see Problems in Transit : Sleep Disturbance (Jet Lag)) could result from taking melatonin derived from animal brains but not from taking artificially produced melatonin. In people who are depressed, melatonin may worsen symptoms. Melatonin is best taken under medical supervision.