Melatonin is a hormone made by the brain. It helps regulate cycles of sleep and wakefulness. As people age, they make less melatonin. Melatonin supplements are dietary supplements, which aren't held to the same standards as prescription drugs by the U.S. government.
Researchers from Canada's University of Alberta reviewed studies published from 1999 to 2003. They found that taking melatonin supplements didn't help people with sleep disorders fall asleep faster or sleep better -- at least not in the studies they reviewed.
The studies focused on sleep, not daytime grogginess, note research associate Nina Buscemi, PhD, and colleagues. They found that while melatonin supplements appeared to be safe, the studies were too short to be sure about that.
The report appears in BMJ Online First.
Late, Restless Sleep
The researchers checked 13 electronic databases for studies on melatonin and sleep disorders stemming from causes such as medical problems, substance misuse, and sleep disorders caused by jet lag, late-night lifestyles, and shift work. They also hand-searched abstracts of meetings from the Associated Professional Sleep Societies.
Here's what they found:
- In 6 trials totaling 97 people, melatonin wasn't found to help people with health-related sleep disorders fall asleep faster.
- In 9 trials totaling 427 people, melatonin wasn't found to help people with sleep problems due to jet lag, late hours, or shift work fall asleep faster.
Melatonin appeared to be safe, but the studies were rather short, so the researchers don't draw any firm conclusions about that. They also weren't thrilled with the quality of the studies they found.
Past research on melatonin has been mixed. In November 2005, a small study suggested that taking melatonin before eastbound travel might ease jet lag. In March 2005, another review of melatonin research found that melatonin supplements might be modestly effective in treating insomnia.
Further studies of melatonin are needed, and those studies should be well designed, write Buscemi and colleagues.