Efficacy of melatonin for chronic insomnia: Systematic reviews and meta-analyses

We conducted systematic reviews and meta-analyses to evaluate the efficacy of melatonin versus placebo or other hypnotic agents in improving sleep quality and quantity in patients with chronic insomnia. A literature search on Ovid-MEDLINE, EMBASE, and the Cochrane Library was performed up to November 2020. Sleep onset latency, total sleep time, sleep efficiency, sleep quality and quality of life were examined as outcomes. We identified 24 randomized controlled trials of chronic insomnia including four studies of patients with comorbid insomnia. All studies were compared with placebo. Due to heterogeneity, we conducted subgroup analyses by age group. In non-comorbid insomnia, melatonin was only significantly effective in sleep onset latency and total sleep time in children and adolescents. In adults group, melatonin was not significantly effective in improving sleep onset latency, total sleep time, and sleep efficiency. In comorbid insomnia, melatonin significantly improved sleep onset latency in all age groups, but there was only one study in adults group. In conclusion, melatonin did not appear to be effective in adults but might be effective in children and adolescents with chronic insomnia for both comorbid insomnia and non-comorbid insomnia. Further studies are needed to establish the efficacy and safety of melatonin by age groups.