Melatonin
Melatonin is the hormone your pineal gland already makes to announce that it's night. Take it as a supplement and it binds MT1 and MT2 receptors in the suprachiasmatic nucleus, nudging you toward sleep onset and shifting your circadian clock's phase. That's a chronobiotic effect, not a sedative knockout. Think less "lights out" and more "resetting the clock on the wall." Timing relative to your body clock decides which direction that shift goes, so when you take it matters as much as whether you do.
Evidence
Strong, well-replicated, no asterisks needed. Multiple meta-analyses of randomized controlled trials show melatonin modestly shortens the time it takes to fall asleep, mildly increases total sleep time, and improves sleep quality overall. The real payoff shows up for circadian disruption: jet lag, delayed sleep-wake phase disorder, shift work. Straightforward insomnia gets a smaller effect, so keep expectations sized to the data.
Interactions
May potentiate sedatives, benzodiazepines, and alcohol (additive drowsiness). Can enhance the effect of anticoagulants and antiplatelet agents, so use caution with warfarin. Fluvoxamine and other CYP1A2 inhibitors markedly raise melatonin levels; caution with several SSRIs/antidepressants. May affect blood pressure and interact with antihypertensives. May lower seizure threshold in some individuals and can affect glucose regulation.
Cautions
Generally well tolerated short term; common effects are next-morning grogginess, headache, and vivid dreams. Over-the-counter product content is often inaccurately labeled. Not a substitute for sleep hygiene. Caution in pregnancy, breastfeeding, autoimmune conditions, and epilepsy; discuss pediatric use with a clinician. This is a neutral reference and not a treatment recommendation.
Food sources
Present in small amounts in some foods including tart cherries, pistachios, walnuts, and certain grains, but dietary quantities are far below typical supplemental doses.
