Table 1.

Clinical trials of melatonin as therapy for fibromyalgia.

Study	n	Dose	Study Design	Results
Citera et al., 2000 [85]	19	3 mg	Pilot	Tender points, pain intensity, and sleep quality improved after 4 weeks
Acuña-Castroviejo et al., 2006 [86]	4	6 mg daily	Pilot	Pain and fatigue improved. Sleep–wake cycle normalized after 15 days
Hussain et al., 2011 [87]	101	5 mg daily/ 3 mg + 20 mg fluoxetine daily/5 mg + 20 mg fluoxetine daily	Double-blind RCT 1	In every case, FIQ 2 score improved. After 8 weeks, combination with fluoxetine was more effective
De Zanette et al., 2014 [26]	63	10 mg daily/10 mg + 25 mg amitriptyline daily	Double-blind RCT 1	On pain and threshold, melatonin was more helpful than amitriptyline alone. Tender points and sleep quality were improved after 6 weeks
Castaño et al., 2018 [77]	33	3, 6, 9, 12, and 15 mg daily	Longitudinal placebo-controlled design	Melatonin doses of 12–15 mg and 6–15 mg enhanced sleep quality, respectively. Melatonin (9–15 mg) for 10 days improved total antioxidant capacity
Castaño et al., 2019 [78]	36	3, 6, 9, 12, and 15 mg daily	Longitudinal placebo-controlled design	After 10 days, pain, happiness, quality of life, anxiety, and FIQ 2 improved

¹ RCT: randomized controlled trial; ² FIQ: fibromyalgia impact questionnaire.