Melatonin and Sleep
The pattern of waking during the day when it is light and sleeping at night when it is dark is a natural part of human life. Only recently have scientists begun to understand the alternating cycle of sleep and waking, and how it is related to daylight and darkness.
A key factor in how human sleep is regulated is exposure to light or to darkness. Exposure to light stimulates a nerve pathway from the retina in the eye to an area in the brain called the hypothala-mus. There, a special center called the supra-chiasmatic nucleus (SCN) initiates signals to other parts of the brain that control hormones, body temperature and other functions that play a role in making us feel sleepy or wide awake.
The SCN works like a clock that sets off a regulated pattern of activities that affect the entire body. Once exposed to the first light each day, the clock in the SCN begins performing functions like raising body temperature and releasing stimulating hormones like cortisol. The SCN also delays the release of other hormones like melatonin, which is associated with sleep onset, until many hours later when darkness arrives.
Because melatonin is a hormone that is part of the human sleep-wake cycle, many people think that by taking more of it as a pill, it will help them to fall asleep faster or stay asleep longer. This brochure will provide more information about melatonin and help you decide whether this is something you should use.
Overall, the National Sleep Foundation (NSF) recommends that if you feel a sleep problem is serious enough to treat, then you should consult your physician first to make sure you understand the cause of your sleep problem and treat it appropriately.
Melatonin is a natural hormone made by your body's pineal (pih-knee-uhl) gland. This is a pea-sized gland located just above the middle of the brain. During the day the pineal is inactive. When the sun goes down and darkness occurs, the pineal is "turned on" by the SCN and begins to actively produce melatonin, which is released into the blood. Usually, this occurs around 9 pm. As a result, melatonin levels in the blood rise sharply and you begin to feel less alert. Sleep becomes more inviting. Melatonin levels in the blood stay elevated for about 12 hours - all through the night - before the light of a new day when they fall back to low daytime levels by about 9 am. Daytime levels of melatonin are barely detectable.
Besides adjusting the timing of the clock, bright light has another effect. It directly inhibits the release of melatonin. That is why melatonin is sometimes called the "Dracula of hormones" - it only comes out in the dark. Even if the pineal gland is switched "on" by the clock, it will not produce melatonin unless the person is in a dimly lit environment. In addition to sunlight, artificial indoor lighting can be bright enough to prevent the release of melatonin.
The amount of melatonin released at night varies among individuals, but it is somewhat related to age. Children on average secrete more melatonin than adults, which decreases further with age. However, research has shown that older people with sleep problems do not always have lower melatonin levels than people who experience normal sleep.
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.
When traveling across time zones, we need to adjust our body clocks from "home time" to the new time. The more time zones we cross, the longer it takes to reset the body clock to the new time. After arriving from a long trip, our body clocks are out of synch with the local time and we feel sleepy, alert and hungry at the wrong times. The problem is compounded by sleep loss during an overnight flight and possibly by alcohol and caffeine consumed on board. These add up to produce "jet lag." Jet lag is not "all in your head." It is a physical condition caused by the disturbance of our circadian rhythms and travel associated with sleep deprivation. An NSF survey found that about half of all business travelers experience jet lag. They report that their performance and productivity are negatively affected. The problem was worse for women than men surveyed.
Although research is very limited, the use of melatonin for jet lag appears reasonable. Many published scientific studies conclude that melatonin can be effective for preventing or reducing jet lag, particularly for crossing five or more time zones and when traveling east. However, safe and appropriate use of melatonin needs further testing.
There is no best cure for jet lag. You can use the power of the sun (or other sources of bright light) to reset your body clock. As a general principle, light exposure in the morning will reset the body clock to an earlier time while light in the evening will reset it to a later time. No matter what you do, it will probably take a few days for your body clock to adjust to a new time zone.
For travel to the east, try adjusting your clock to an earlier sleep time so you get up as early as you can and get out in the morning sun. Before your clock is adjusted to the new time zone, getting to sleep in the evening can be difficult. Be sure to avoid alcohol and caffeine at least three to four hours before you go to bed. Save the (caffeine-filled) chocolate on your pillow for a daytime snack.
If you are traveling west, try to get at least an hour's worth of morning sunlight the first chance you can after you reach your destination. And before you travel, try waking and going to sleep an hour later for each time zone you'll cross. For example, for a trip from New York to California, try to shift your bed and wake an hour later for each of three days before you leave - instead of sleeping from 11 pm to 7 am, sleep from midnight to 8 am, then 1 am to 9 am, and on the third night, from 2 am to 10 am.
Delayed Sleep Phase Syndrome
Jet lag isn't the only disorder of circadian rhythms. People with Delayed Sleep Phase Syndrome (DSPS) are only able to fall asleep late into the night or early in the morning. Although rare in adults, the syndrome is quite common among adolescents. Several studies suggest that melatonin may be of help for this condition. However, exposing yourself to light when you want to be awake may be just as helpful.
Copyright Notice: All materials contained on this site are protected by United States copyright law and may not be reproduced, distributed, transmitted, displayed, published or broadcast without the prior written permission of the National Sleep Foundation. You may not alter or remove any trademark, copyright or other notice from copies of the content. Links to Web sites other than those owned by the National Sleep Foundation are offered as a service to readers and the foundation is not responsible for their content. Click here to request permission.
Advertisement Notice: The National Sleep Foundation neither control nor endorse the advertisements, items or Websites featured in the advertisers links on our Web pages.