FRIDAY, Feb. 10 (HealthDay News) -- Melatonin, the widely used over-the-counter hormone supplement, isn't effective as a sleeping pill if your insomnia is caused by an underlying condition, according to a new Canadian review.
It won't help prevent or ease jet lag, either, claims the report in the Feb. 10 issue of the British Medical Journal.
The study doesn't conclude that melatonin is of no use at all as a sleep aid, added study author Nina Buscemi, a research associate in the University of Alberta Department of Pediatrics.
"We looked at a specific subset of sleep disorders, those accompanied by other medical or psychiatric disorders such as depression or drug abuse," she said.
The supplement also doesn't appear to do any harm to those who take it, the researchers added.
The number of participants in the studies that were analyzed in the report was relatively small -- 97 people in six studies focused on sleep trouble related to specific disorders, 427 people in nine studies focused on "sleep restriction" due to jet lag or shift work, and 651 people involved in 17 safety-related studies.
"We are talking about a small sample size," she said. "If someone published a much larger study tomorrow, it might change our conclusions."
Buscemi said she can't give advice to people wondering whether melatonin will help their insomnia because she's not a physician.
"I'm not in a position to make a treatment recommendation," she said. "I can only tell you what the evidence shows -- and the evidence is lacking."
One physician is ready to make a recommendation about melatonin, at least when it comes to elderly individuals who can't sleep.
Dr. Richard J. Wurtman, a distinguished professor of neuropharmacology at the Massachusetts Institute of Technology, said older people often have trouble getting to sleep because the pineal gland, where melatonin is produced, "gets calcified with age." Taking a little bit of the hormone makes up for the pineal gland's weakness, he explained.
In 2001, Wurtman and his colleagues published a study in the Journal of Clinical Endocrinology and Metabolism that suggested that small doses of melatonin -- no more than 0.3 milligrams -- could help older people conquer insomnia.
But it's got to be just this little bit, Wurtman said, because too much melatonin overwhelms and deactivates receptors that transfer the hormone into cells.
Wurtman noted that the Alberta study used doses as high a 6 milligrams. "They are giving 20 times the correct dose," he said. "The higher the dose we gave, the lower the response we got."
Most of the melatonin products now on the market give similar overdoses, Wurtman said. The result: "Your insomnia gets worse after a while," he said. "What you need is low doses that raise blood levels to where they were when they were young. It's the equivalent of hormone replacement therapy for women."
Wurtman added that he does have a personal stake in this debate, since MIT has a patent on the use of low-dose melatonin for sleep. "We have a spate of articles showing our product is better," Wurtman said.
A rundown on melatonin is given by the American Academy of Family Physicians.