Melatonin
Melatonin is a hormone that is secreted by a small gland in the center of the brain called the pineal gland. At birth there is very little melatonin secreted by this gland. It is not present until about 3 months of age. At that time, the nighttime peak of melatonin increases dramatically and reaches its peak at about 2 to 3 years of age. Then, it gradually decreases with age. Elderly people often seem to have a difficult time sleeping and it is hypothesized that this is because of the decreased secretion of melatonin.
Pineal stores of melatonin are typically released into circulation when illumination diminishes, and may help explain why most of us sleep better when the lights are off. The melatonin level in the blood peaks in the middle of the night and decreases rapidly as we wake and are exposed to sunlight in the morning. Melatonin levels may drift in blind people, although there seems to be a circadian rythm of melatonin levels even in the absence of visual clues. Orally administered melatonin has been shown to promote sleep.
Melatonin preparations are available without prescription in health food stores and pharmacies. Commercially available preparations usually come in 2.5 or 3 milligram (mg) tablets, and a young child should do well on a third of this amount. The higher amounts will produce deeper sleep, but the hormone may still be circulating at quite high levels in the morning, and there are reasons to believe that is undesirable.
Melatonin usually does not diminish in its effects even with prolong use, but for unknown reasons, this is not the case in all individuals. If a low dose of melatonin that has been effective for some time seems to be losing its effect (i.e., tolerance is setting in), one is wiser to stop taking the supplement for a while rather than increasing the dose.
Although we do know that melatonin and sleep have many bodily benefits, we do not have adequate evidence about the many "hows and whys." Our knowledge of such matters has not progressed much beyond Shakespeare's speculation that the function of sleep is "to knit up the raveled sleeve of care" even though modern thinkers are more likely to suggest that "sleep restores brain neurochemistries and other bodily resources that have been depleted by waking activities." Melatonin appears to be a prime guardian of such restorative processes, and without it, our lives become raveled indeed.