SYSTEMATIC REVIEW OF MELATONIN SUPPLEMENTATION AND SLEEP OUTCOMES ACROSS ADULT POPULATIONS
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Keywords
melatonin, sleep quality, randomized controlled trials, circadian rhythm, systematic review
Abstract
Background: Sleep disturbances affect nearly one-third of adults, contributing to adverse health outcomes. Melatonin, an endogenous circadian regulator, is widely used as a supplement, yet evidence on its efficacy across diverse adult populations remains heterogeneous.
Methods: This systematic review (PRISMA 2020, OSF preregistered) included randomized controlled trials of oral melatonin versus placebo in adults. Eight RCTs (1,847 participants) were synthesised narratively due to substantial clinical and methodological heterogeneity. Outcomes included sleep quality, onset latency, total sleep time, and efficiency.
Results: Melatonin consistently improved subjective sleep quality (5 studies, moderate-certainty evidence) and reduced sleep onset latency (4 studies, moderate certainty). Benefits on total sleep time and efficiency were modest with low certainty. Effects were more pronounced in neurological populations (Parkinson’s disease, cognitive impairment) and when administered 1–2 hours before bedtime. Higher doses (>4 mg) and immediate-release formulations showed favourable trends. Melatonin also reduced delirium in critically ill patients (low certainty) and had a safety profile comparable to placebo.
Conclusion: Melatonin supplementation is associated with improved sleep quality and initiation, particularly in conditions involving circadian dysregulation. However, heterogeneity and modest effect sizes warrant individualised use and further rigorous trials.
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Taranjot Kour
Assistant Professor, Physiology, Shri Mata Vaishno Devi Institute of Medical Excellence, Katra
Poonam Kalsi
Assistant Professor, Physiology, Government Medical College, Kathua
Moin Manzoor
Post Graduate Student, Physiology, All India Institute of Medical Sciences, New Delhi
