Table 1.

Bias assessment for included tDCS studies on fibromyalgia (n = 14) [28,29,30,31,32,33,34,35,36,37,38,39,40,41] using the Cochrane risk of bias tool.

	Fregni et al. (2006) [28]	Valle et al. (2009) [29]	Riberto et al. (2011) [30]	Mendonca et al. (2011) [31]	Fagerlundet al. (2015) [32]	Jales et al. (2015) [33]	Khedr et al. (2017) [34]	To et al. (2017) [35]	Brietzke et al. (2020) [36]	De Melo et al. (2020) [37]	Caumo et al. (2022) [38]	Samartin-Veiga et al. (2022) [39]	Loreti et al. (2023) [40]	Caumo et al. (2023) [41]	+ Low Risk of Bias
															? Uncertain Risk of Bias
															− High Risk of Bias
Selection bias: Random sequence generation	?	?	?	?	+	?	+	?	+	+	+	+	+	+	57.14% low, 42.8% uncertain, 0% high
Selection bias: Allocation concealment	+	?	?	+	?	+	?	?	+	?	+	+	+	+	57.14% low, 42.8% uncertain, 0 % high
Reporting bias: Selective reporting	+	−	+	+	+		+	+	+	+	+	+	+	+	92.9% low, 0% uncertain, 7.1% high
Performance bias: Blinding (participants and personnel)	+	+	+	+	+	+	+	?	+	+	+	+	+	+	92.9% low, 7.1% uncertain, 0% high
Detection bias: Blinding of outcome assessment	+	+	+	+	+	+	+	?	+	?	+	+	+	+	85.8% low, 14.2% uncertain, 0% high
Attrition bias: Incomplete outcome data	+	+	+	+	+	+	−	−	+	−	+	+	+	+	78.6% low, 0% uncertain, 21.4% high
Other bias	+	+	+	+	+	+	−	+	+	−	+	+	+	+	85.8% low, 0% uncertain, 14.2% high