Table 2.

Risk of bias assessment for the included papers.

Authors	Random sequence generation (selection bias)	Allocation concealment (selection bias)	Blinding of participant and personnel (performance bias)	Blinding of outcome assessment (detection bias)	Incomplete outcome data (attrition)	Selective reporting (reporting bias)	Co-interventions	Intention to treat analysis	Group similarity at baseline	Compliance	Timing of outcome assessments	Other biases	Score	Conclusion
Rim et al8	?	?	−	?	?	?	?	?	?	?	−	−	3	High
McMillen et al7	?	?	?	−	?	?	?	?	?	?	−	−	3	High
Oei et al19	?	?	?	?	?	?	?	?	?	?	?	−	1	High
West et al5	?	?	−	?	?	?	?	?	+	?	−	−	3	High
Fillmore et al17	?	?	−	−	?	+	+	?	+	?	+	−	3	High
Rakauskas et al9	?	?	+	?	?	?	+	?	+	?	−	−	2	High
Marczinski et al3	?	?	+	+	+	+	?	?	+	?	−	−	2	High
Huemer et al18	?	?	+	−	+	+	?	+	+	?	?	−	2	High
Liu et al2	?	?	+	?	?	?	?	?	?	?	+	−	1	High
Howland et al10	?	?	+	+	?	+	+	?	+	?	?	−	1	High
Spaanjaars et al4	?	?	+	?	−	?	+	?	?	?	−	−	3	High
Simons et al11	?	?	+	?	−	+	+	+	+	?	−	−	3	High
Veldstra et al5 Study 1	?	?	+	?	−	?	?	?	?	?	−	−	3	High
Veldstra et al6 Study 2	?	?	+	?	−	?	+	?	?	?	−	−	3	High

Note: The sign “?” means unclear risk of bias, the sign of “−” means low risk of bias and the sign of “+” means high risk of bias.