Melatonin is a hormone released by the pineal gland in the brain around sunset, sending a signal to our bodies to be ready for sleep a few hours after the sun goes down. Upon the release of melatonin, our bodies prepare for rest in a few ways — such as lowering our brain temperature and increasing our sleepiness.
Our brain continues to secrete melatonin throughout the night, peaking around 2 to 4am. When morning comes, melatonin production stops. Cortisol gets released instead, which boosts our bodies’ wakefulness. This rise and fall of our melatonin and cortisol levels is part of our circadian rhythm, and helps us regulate our sleep-wake cycle.
Takeaway: Melatonin tells our bodies when to fall asleep based on daylight hours, but it won’t make us sleepier, or make sleep come any faster.