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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, however, 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. On a non-blinded small series with elderly insomniacs, your editor has 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. fp