Comments: Until more is known about melatonin's long-term effects, my recommendations are to use small doses of this hormone for sleep in the range of 0.3 to 1 mg and not to exceed the use of this hormone more frequently than two or three nights a week. Many people become tolerant to the sleep inducing effects of melatonin when they use it too frequently. Unfortunately, we don't know at this time whether small amounts of melatonin used for sleep purposes provides any significant antioxidant protection. It's possible that larger amounts of melatonin offer more antioxidant protection but then we run the risk of unknown long-term side effects from high dosage use for prolonged periods.

Reiter RJ. Oxidative damage in the central nervous system: protection by melatonin. Prog Neurobiol 1998 Oct;56(3):359-84