Table 1.

Risk of bias of included studies.

Author	Random sequence generation (selection bias)	Allocation concealment (selection bias)	Selective reporting (reporting bias)	Blinding (performance bias)	Incomplete outcome data (attrition bias)	Other sources of bias (other bias)	Overall decision on quality of study
Abelson et al.5	Low	Low	Low	Low	Low	Low	Low
Bremond-Gignac et al.6	Low	Low	Low	Low	Low	Low	Low
Cochereau et al.11	Low	Low	Low	Low	Low	Low	Low
Denis et al.12	Low	Low	Low	Low	Low	Low	Low
Protzko et al.13	Low	Low	Unclear	Low	Low	Low	Moderate
Robert et al.14	Low	Low	Low	Low	Low	Low	Low
Bakar Demircay et al.8	Low	Unclear	Low	Low	Low	Low	Low
Haque et al.7	Low	Low	Low	Low	Low	Low	Low
Luchs15	Low	Low	Low	Low	Low	Low	Low
Yildiz et al.16	Low	Low	Low	Low	Low	Low	Low
Opitz and Tyler17	Low	Low	Low	Low	Low	Low	Low