Melatonin is a naturally occurring hormone found in most animals, including humans. Circulating levels vary in a daily cycle, and melatonin is important in the regulation of the circadian rhythms of several biological functions including sleep. The use of melatonin as a drug can synchronize the circadian clock to environmental cycles and can have beneficial effects for treatment of certain insomnias.
Production of melatonin in the body is inhibited by light and permitted by darkness. For this reason melatonin has been called “the hormone of darkness” and its onset each evening is called the Dim-Light Melatonin Onset (DLMO) which caused Sleep Disturbances. Secretion of melatonin as well as its level in the blood, peaks in the middle of the night, and gradually falls during the second half of the night, with normal variations in timing according to an individual’s chronotype. For this reason supplementation with melatonin, can induce sleep without a ‘hangover’ effect the next day.