Melatonin is a hormone produced in the brain that helps regulate your sleep and wake cycle. Your body has its own internal clock that controls your natural cycle of sleeping and waking hours. In part, your body clock controls how much melatonin your body makes. Normally, melatonin levels begin to rise in the mid- to late evening, remain high for most of the night, and then drop in the early morning hours. Natural melatonin levels slowly drop with age. Some older adults make very small amounts of it or none at all. Melatonin is effective in treating sleep disorders, jet lag and insomnia and it is also possibly effective in treatinghigh blood pressure, tumors, low blood platelets (blood cells that help your blood to clot) and anxiety. A topical form of melatonin applied to the skin is possibly effective in preventing sunburn.