de Zanette 2014.

Study characteristics
Methods	Design: parallel Duration: 6 weeks Assessment: baseline and post‐intervention Country: Brazil
Participants	Pain condition: fibromyalgia Population: women with fibromyalgia Minimum pain intensity: ≥ 50 on 0‐100 VAS Inclusion criteria Women with fibromyalgia matching ACR criteria Pain intensity of ≥ 50 on 0‐100 VAS Exclusion criteria Physical health comorbidities BMI > 35 Total participants randomised: 63 Age in years (mean): 48.9 Gender: 63/63 were female Pain duration in years (mean, SD): NR
Interventions	Melatonin 10 mg n = 21 Hormone Identical appearance Double‐dummy to match combined arm Amitriptyline 25 mg n = 21 TCA Fixed dose, no titration Double‐dummy to match combined arm Melatonin 10 mg + amitriptyline 25 mg n = 21 Hormone and TCA antidepressant Fixed doses, no titration
Outcomes	Pain intensity Quality of life Sleep AEs Withdrawal
Missing data methods	ITT with LOCF
Funding source	Non‐pharmaceutical ‐ multiple Brazilian governmental agencies
Conflicts of interest	The authors declare that there are no financial or other relationships that might lead to CoIs involving any of the following arrangements: financial relationship to the work, employees of a company, consultants for a company, stockholders of the company, members of a speakers' bureau or any other form of financial compensation.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Randomisation methods: NR
Allocation concealment (selection bias)	Low risk	Sealed, sequentially numbered envelopes
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Double‐blind, double‐dummy trial, identical appearance of tablets
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Self‐reported outcomes from blinded participants
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	States ITT but no method of imputation specified. Low attrition Attrition Total: 6/63 (9.5%) Melatonin 10 mg: 2/21 (9.5%) Amitriptyline 25 mg: 2/21 (9.5%) Melatonin + amitriptyline: 2/21 (9.5%)
Selective reporting (reporting bias)	Low risk	Outcomes match those listed on trial registration
Other bias	Low risk	No other sources of bias were identified.