Melatonin for Circadian Rhythm & Sleep — Brain
Endogenous pineal hormone and chronobiotic agent with strong evidence for sleep onset latency reduction and circadian rhythm disorders.
Overview
Melatonin (N-acetyl-5-methoxytryptamine) is an endogenous hormone synthesized from serotonin in the pineal gland, with production rising dramatically in the evening in response to darkness (regulated by the suprachiasmatic nucleus) and suppressed by light exposure. It is the primary chronobiotic signal in the human circadian system. Melatonin binds to MT1 and MT2 G-protein-coupled receptors in the suprachiasmatic nucleus (SCN) and throughout the body, promoting sleep onset, regulating circadian phase, and exerting antioxidant and immunomodulatory effects. The strongest clinical evidence supports melatonin for reducing sleep onset latency (meta-analyses show 7-12 minute reduction), improving sleep quality, and treating circadian rhythm sleep-wake disorders including delayed sleep-wake phase disorder, jet lag, and shift work disorder. The American Academy of Sleep Medicine conditionally recommends melatonin for delayed sleep-wake phase disorder. Exogenous melatonin at doses as low as 0.3-0.5 mg effectively shifts circadian phase when timed appropriately (5-7 hours before habitual sleep onset). Higher doses (3-10 mg) have mild direct soporific effects but are not more effective for chronobiotic purposes. Melatonin production declines with age, with some studies showing 50-80% reduction by age 60-70, which may contribute to age-related sleep disruption. Unlike conventional hypnotics, melatonin does not produce dependence, tolerance, or rebound insomnia upon discontinuation.
Indications
- Strong evidence: Sleep onset latency reduction (meta-analysis confirmed)
- Strong evidence: Delayed sleep-wake phase disorder (AASM recommendation)
- Strong evidence: Jet lag prevention and treatment
- Moderate evidence: Shift work sleep disorder
- Moderate evidence: Pediatric sleep onset insomnia (including ASD)
- Moderate evidence: Perioperative anxiolysis (premedication alternative)
Mechanism of Action
Melatonin binds to MT1 and MT2 G-protein-coupled receptors in the SCN, reducing neuronal firing rate and promoting sleep-permissive states
Dosing
| Compound | Dose | Frequency | Notes |
|---|---|---|---|
| Melatonin (immediate-release) | 0.3-0.5 mg | 30-60 minutes before desired bedtime | Chronobiotic (phase-shifting) dose; physiologic replacement |
| Melatonin (immediate-release) | 1-3 mg | 30-60 minutes before bedtime | Standard OTC dose for sleep onset support |
| Melatonin (extended-release) | 2 mg | 1-2 hours before bedtime | Prolonged-release for sleep maintenance (Circadin in EU) |
| Melatonin | 0.5-5 mg | Timed for destination bedtime | Jet lag protocol; take at destination bedtime for 3-5 nights |
Evidence Grade
GRADE B
Safety & Contraindications
- Generally well tolerated with excellent safety profile at standard doses (0.5-5 mg)
- Daytime drowsiness, headache, dizziness most common side effects
- Does NOT produce tolerance, dependence, or rebound insomnia upon discontinuation
- May interact with anticoagulants (warfarin), antidiabetic medications, and immunosuppressants
- Exogenous melatonin at high doses does NOT suppress endogenous production
- Unregulated supplement quality in the US — actual content varies 83% from label claims (Journal of Clinical Sleep Medicine)
- Use caution in autoimmune conditions (melatonin is immunostimulatory)