Melatonin is a hormone produced in the pineal gland, a small gland in the brain. Melatonin is involved in regulating circadian rhythms, the regular daily cycles of the body such as sleeping and waking. Blood levels of melatonin are high at night and low during the day.
Many therapeutic benefits have been claimed for melatonin. Most studies have evaluated its effects on sleeping problems. For insomnia, some, but not all, clinical investigations have shown a therapeutic effect with melatonin. Studies of another sleep disorder, jet lag, have produced mixed results. No studies strongly support the use of melatonin treatment for cancer.
A possible role of melatonin in causing MS has been proposed. In one study, high blood levels of melatonin were associated with a later age of onset of the disease and a shorter duration of the disease. The significance of these findings in relation to melatonin causing MS or the effect of taking melatonin supplements on MS is not known