Melatonin is a natural, non-addicting hormone supplement that assists with sleep.
Your body has its own internal clock that controls your natural cycle of sleeping and waking hours. In part, your body clock controls how much melatonin your body makes. Normally, melatonin levels begin to rise in the mid- to late evening, remain high for most of the night, and then drop in the early morning hours.
Light affects how much melatonin your body produces. During the shorter days of the winter months, your body may produce melatonin either earlier or later in the day than usual. This change can lead to symptoms of seasonal affective disorder (SAD), or winter depression.
Natural melatonin levels slowly drop with age. Some older adults make very small amounts of it or none at all.
Chances are good that you have seen melatonin in health food stores or in an advertisement or article. No other hormone is available in the United States without a prescription. Because melatonin is contained naturally in some foods, the U.S. Dietary Supplement Health and Education Act of 1994 allows it to be sold as a dietary supplement (e.g., vitamins and minerals). These do not need to be approved by the Food and Drug Administration (FDA) or controlled in the same way as drugs.
Because it is not categorized as a drug, synthetic melatonin is made in factories that are not regulated by the FDA. Listed doses may not be controlled or accurate, meaning the amount of melatonin in a pill you take may not be the amount listed on the package. Most commercial products are offered at dosages that cause melatonin levels in the blood to rise to much higher levels than are naturally produced in the body. Taking a typical dose (1 to 3 mg) may elevate your blood melatonin levels to 1 to 20 times normal. Side effects do not have to be listed on the product's packaging. Yet, fatigue and depression have occasionally been reported with use of melatonin.
When given to animals, melatonin can cause changes in blood pressure and affect fertility. Such effects in humans would be a medical risk for people with heart-related problems, hypertension and stroke, kidney disease and sleep apnea as well as for women of child-bearing age.
For melatonin to be helpful, the correct dosage, method and time of day it is taken must be appropriate to the sleep problem. Taking it at the "wrong" time of day may reset your biological clock in an undesirable direction. How much to take, when to take it, and melatonin's effectiveness, if any, for particular sleep disorders is only beginning to be understood.
While there are real concerns about the widespread use of melatonin sold as a consumer product, there have not been any reported cases of proven toxicity or overdose.
For some people, melatonin seems to help improve sleep. However, when scientists conduct tests to compare melatonin as a "sleeping pill" to a placebo (sugar pill) most studies show no benefit of melatonin. Evidence that melatonin can reset the body clock is more well established, although it is not clear whether exposure to light may be more effective. Overall, research indicates improved sleep when melatonin is taken at the appropriate time for jet lag and shift work. Appropriate dosage and any safety risks will become clear with further research.
Some studies show promise for the use of melatonin in shortening the time it takes to fall asleep and reducing the number of awakenings, but not necessarily total sleep time. Other studies show no benefit at all with melatonin.
Melatonin might help shift workers on irregular shifts who need to adjust their schedules. When taken in low doses at the appropriate time, melatonin can help advance or delay the sleep-wake cycle. The effect can last for six hours. When taken in the morning, it may cause fatigue and reduced reaction time, reduced vigilance and decreased vigor during the day.
When melatonin was given to people near their normal sleep time, the results differed from one study to the next. When given during the day, it promotes drowsiness and shortens sleep onset.
Of the few studies involving people with insomnia, results are inconclusive. One study of people over 50 years of age found that taking melatonin restored their sleep efficiency and improved their sleep. Other studies have demonstrated that, although sleep onset was improved, melatonin did not help people stay asleep or stay alert during the day.
Large studies are needed to demonstrate if melatonin is effective and safe for some forms of insomnia, particularly for long-term use. It may be true that melatonin is effective and safe for some types of insomnia and for children but not for other types of sleep problems. How much to take, when to take it and its effectiveness, if any, for particular disorders is only beginning to be understood.