The available pharmacological modalities for the treatment of fibromyalgia (FM) are associated with a variety of adverse effects and limited benefits. In this study, we systematically reviewed the impact of melatonin in the treatment of FM.

Interventional studies, either controlled or uncontrolled and randomized or non-randomized, were included. PubMed, EMBASE, Scopus, Web of Science, and the Cochrane Library were searched without time limitation. Primary outcome measures were the effect of melatonin on the disease impact, pain, sleep quality, tender point count, fatigue, anxiety, stiffness, and depression in FM patients. Four studies, reporting the effect of melatonin on 98 patients, were eligible to include. All the studies reported the positive effect of melatonin on the FM symptoms. No major adverse event was reported. A significant level of heterogeneity was observed between the studies. Therefore, further high-quality controlled clinical trials are needed to understand the role of melatonin in FM treatment fully.