This is the 2007 version. Click here for the 2017 chapter 03 table of contents.

Melatonin and Sleep

The chemical melatonin is produced by the pineal (pie-NEE-al) gland. When melatonin levels in the bloodstream are high, people fall asleep relatively easily. The production of melatonin in the brain is regulated by a structure in the hypothalamus (the suprachiasmatic nucleus) that receives inputs from the eyes. Daylight suppresses melatonin release, so ordinarily people do not fall asleep easily in the daytime—except for a drowsy time in the middle of the afternoon.

How does melatonin relate to sleep?

Melatonin production increases around 9:30 p.m. in older adults, 10:30 p.m. in adolescents. Most people can fall asleep quickly at that time. People with a sleep disorder called the "delayed sleep phase syndrome," who typically fall asleep around 4 or 5 a.m., can often be helped by taking a small dose of melatonin around 10 in the evening (Haimov & Lavie, 1996).

The single hour difference in melatonin release between adolescents (10:30 p.m.) and older adults (9:30 p.m.) is actually quite significant because it is an average difference. It points to consistent differences in sleep patterns between adolescents and older people. Adolescents are comfortable staying up later, and they have a harder time getting going in the morning.

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