Melatonin works to regulate your body’s circadian rhythm. Your circadian rhythm is your body’s internal clock; it lets you know when it’s time to sleep, wake and eat. Melatonin also binds to receptors in the body to help you relax. For instance, melatonin binds to receptors in the brain to help reduce nerve activity. In the eyes, it can help reduce dopamine levels, a hormone that helps you stay awake.
Melatonin levels start to rise in your body when it is dark outside, signaling to your body that it is time to sleep. Conversely, light suppresses melatonin production. As melatonin helps your body prepare for sleep, people who don’t make enough of it at night can struggle to fall asleep. There are many factors that may cause low levels of melatonin production at night including stress, smoking, exposure to too much light at night (including blue light), not getting enough natural light during the day, shift work and aging.
Evidence shows that taking melatonin before bed can help you get to sleep. In an analysis of 19 studies on people with sleep disorders, scientists found that melatonin helped reduce the time it took to fall asleep by an average of 7 minutes. In many of these studies, people also reported significantly better quality of sleep [7].