Table 2.

Risk of bias results for the studies using the OHAT rating tool.

Authors	Selection bias	Confounding bias	Performance bias	Attrition bias	Detection bias	Selective reporting bias
Glauser et al. [47]	−	+	−	++	−	+
Schupbach and Glauser [48]	−−	+	−	+	−	+
Wennerberg et al. [41]	++	++	+	+	+	++
Göthberg et al. [42]	++	+	++	+	++	+
Raes et al. [43]	++	++	+	+	−	++
Hall et al. [44]	++	++	+	++	+	++
Dib-Zaitum et al. [45]	++	+	++	++	−	++
Farrag and Khamis [46]	++	++	+	++	+	+
Ungersböck et al. [40]	−	+	−	−	+	++
Susin et al. [35]	++	++	+	++	++	++
Fukayo et al. [37]	−	−	−	+	−	++
Rossi et al. [36]	−	++	−	+	+	+
Areva et al. [39]	+	+	−	+	−	+
Paladan et al. [38]	+	+	−	−	−	+
Welander et al. [34]	−	−	−	+	+	+

Note: “++”: definitely low risk of bias; “+”: probably low risk of bias; “–”: probably high risk of bias; and “– –”: definitely high risk of bias.