• melatonin;
  • sleep;
  • primary;
  • review

Background: Exogenous melatonin has been increasingly used in the management of sleep disorders.

Purpose: To conduct a systematic review of the efficacy and safety of exogenous melatonin in the management of primary sleep disorders.

Data Sources: A number of electronic databases were searched. We reviewed the bibliographies of included studies and relevant reviews and conducted hand-searching.

Study Selection: Randomized controlled trials (RCTs) were eligible for the efficacy review, and controlled trials were eligible for the safety review.

Data Extraction: One reviewer extracted data, while the other verified data extracted. The Random Effects Model was used to analyze data.

Data Synthesis: Melatonin decreased sleep onset latency (weighted mean difference [WMD]: −11.7 minutes; 95% confidence interval [CI]: −18.2, −5.2)); it was decreased to a greater extent in people with delayed sleep phase syndrome (WMD: −38.8 minutes; 95% CI: −50.3, −27.3; n=2) compared with people with insomnia (WMD: −7.2 minutes; 95% CI: −12.0, −2.4; n=12). The former result appears to be clinically important. There was no evidence of adverse effects of melatonin.

Conclusions: There is evidence to suggest that melatonin is not effective in treating most primary sleep disorders with short-term use (4 weeks or less); however, additional large-scale RCTs are needed before firm conclusions can be drawn. There is some evidence to suggest that melatonin is effective in treating delayed sleep phase syndrome with short-term use. There is evidence to suggest that melatonin is safe with short-term use (3 months or less).