Melatonin is a hormone produced by the brain's pineal gland to regulate the sleep cycle. Melatonin levels rise in the evening, setting the stage for sleep. Levels subside in the morning, inducing wakefulness.
At least, that's how it's supposed to work. But up to one-fifth of Americans don't get a good night's rest.
Sleep disorders affect 50 million to 70 million people. Insomnia, the most common sleep disorder, plagues up to 12% of adults, say researchers. Children can also be affected. Up to 25% of U.S. kids have sleep problems.
Poor sleep can wear anyone down. It's also dangerous. Drowsy driving causes 100,000 motor vehicle accidents annually, killing 1,550 people and injuring 40,000, says the National Highway Traffic Safety Administration.
Seeking better sleep, many people have tried melatonin supplements. But that strategy may not work.
In the new report Terry Klassen, MD, MSc, FRCPC, of Canada's University of Alberta Evidence-Based Practice Center reviewed more than 130 studies on melatonin and sleep disorders.
Safe, but Does Melatonin Work?
Klassen and colleagues found that while melatonin may be safe for short-term use (for days or weeks), it's not particularly effective.
One exception may be delayed sleep phase syndrome.
People with that condition have a hard time falling asleep before the wee hours of the night and also have trouble waking in the morning. Short-term melatonin use could help with that particular sleep disorder, say the researchers. This is a long-term problem and different from jet lag, a similar short-term problem.
Overcoming Jet Lag?
The experts also saw no signs that melatonin corrects sleep problems from shift work or jet lag. But earlier this year, a different study found that melatonin helps offset jet lag.
In that study, a small group of U.S. Air Force Reservists took slow-release caffeine, 5 milligrams of melatonin, or a placebo the evening before an overseas flight and for the next four evenings. They flew across seven time zones between Texas and France without napping en route. When they landed, melatonin improved sleep quality, but participants still felt sleepy during the day.
The agency's 300-page report doesn't dismiss melatonin. Instead, the researchers call for more studies on topics including melatonin's long-term effects and various supplement formulations.