Melatonin is a hormone produced by a small gland in the brain to help the body regulate the natural cycle of sleeping and waking. Small amounts of melatonin are found in some foods, and it is also available in dietary supplements.

Light affects how much melatonin your body produces. During the shorter days of the winter months, your body may produce melatonin either earlier or later in the day than usual. This change can lead to symptoms of seasonal affective disorder (SAD), or winter depression.

Melatonin is used to treat jet lag and insomnia. A low dose taken at a certain time during the day may also ease symptoms of SAD.

Melatonin supplements are generally safe for short-term use. The safety and effectiveness of long-term use are still being studied.