Melatonin

Melatonin is a hormone produced primarily by the pineal gland in response to darkness, signaling biological night to peripheral tissues and modulating circadian rhythm, sleep, immune function, and antioxidant activity. Endogenous melatonin rises in the evening (typically 2 hours before habitual sleep), peaks in the middle of the night, and declines by morning. Light exposure, particularly blue wavelengths, suppresses melatonin production; this is why evening screen use affects sleep onset.

Supplemental melatonin has two distinct clinical uses. For sleep onset, immediate-release 0.3-0.5mg taken 30-60 minutes before intended sleep time produces modest reductions in sleep onset latency (approximately 10-15 minutes) without the morning grogginess associated with higher doses. For circadian phase advance (moving the biological clock earlier, as in delayed sleep phase syndrome or jet lag recovery eastward), 0.3-0.5mg taken 3-5 hours before habitual sleep time shifts the clock approximately 30-60 minutes earlier per week of consistent use. This indication requires timing more than dose: high doses do not shift the clock faster.

Most commercial melatonin products are 10-30 times higher than physiologically optimal doses. High-dose melatonin (3-10mg) produces supraphysiological blood levels persisting into morning, causing morning grogginess and potentially suppressing endogenous production with chronic use. Low-dose long-term use has been studied safely in children with ADHD and adults with delayed sleep phase syndrome for multi-year periods. Safety considerations include theoretical concerns in autoimmune disease (melatonin has immune-modulating effects), caution in pregnancy unless medically supervised, and awareness that many commercial products contain doses substantially different from label claims in independent testing.