Effects of Melatonin in Humans

ABSTRACT & COMMENTARY

Synopsis: Contrary to widespread skepticism, melatonin has been shown to shorten sleep onset time and to increase both the efficiency and duration of sleep.

Source: Brzezinski A. N Engl J Med 1997;336:186-195.

Melatonin, which the pineal gland secretes when the retinal photoreceptors turn off during darkness, is generated from serotonin under the influence of the hypothalamic suprachiasmatic nucleus. Brzezinski reviews and summarizes its possible biologic functions which, with the exception of its sometimes disputed soporific effects, remain uncertain in clinical importance. These include action as a putative free radical scavenger, an enhancer of immune function, and a stimulator of reproduction and other processes of equivocal functional requirement.

Contrary to widespread skepticism, nine double-blind, placebo-controlled studies amounting to 120 subjects found that melatonin appears to shorten sleep onset time, to increase the "efficiency" (i.e., the satisfaction) of sleep, and, to a lesser degree, increase the duration of sleep. Some evidence suggests that melatonin particularly improves sleep difficulties in the elderly, but only meager evidence supports the point.

COMMENT BY FRED PLUM, MD

In a non-blinded small series with elderly insomniacs, I have found that 3 mg of melatonin given about an hour before retiring improves both the sleep dimensions mentioned above.

Several studies also report that melatonin in 5 mg doses reduces the symptoms of jet lag if the drug is started at the person’s usual bedtime at the site of arrival and is continued daily for five subsequent days. The author warns that many melatonin products on the market lack FDA approval and have questionable purity. (Dr. Plum is Neurologist-in-Chief, New York Hospital, Cornell Medical Center.)