What it is
Regulatory status: medication in the UK and much of the EU; dietary supplement in the United States
Mechanism evidence: human
At a glance
What it is, why people use it, the evidence, and what to know before trying it.
Why people use it
- Faster sleep onset / shorter sleep-onset latency (SOL) in primary / chronic insomnia.
- Better sleep quality (subjective scales; Circadin “quality of sleep + morning alertness” composite).
- Longer total sleep time (TST) and higher sleep efficiency.
- Better sleep in adults ≥55 with age-related insomnia (the Circadin-labelled population).
- Less subjective jet-lag after crossing several time zones, especially eastward.
- Faster sleep at destination bedtime; less daytime fatigue after the flight.
- Advance of DLMO and clock-hour of sleep onset in DSWPD.
- Entrainment in sighted or blind non-24-hour sleep-wake disorder.
- Longer daytime sleep after a night shift (shift-work disorder).
- Lower oxidative stress / better mitochondrial function in otherwise well adults.
Evidence at a glance
Melatonin is a real hormone with two well-supported **human** jobs: a **chronobiotic** (jet lag after ≥5 time zones; delayed sleep-wake phase; non-24 in blind adults) and a **small soporific** (SOL shorter by roughly **4–11 minutes** in primary-sleep metas; Circadin PR **2 mg** helps a minority of **≥55-year-olds** on a quality-plus-morning-alertness composite). It is **not** a first-line chronic-insomnia hypnotic: AASM 2017 is a **WEAK recommendation against** it for adult sleep-onset or sleep-maintenance insomnia, and the absolute effects are below what that guideline called clinically important.