Table 2.
Risk of bias of individual studies according to the Cochrane guideline
| Study | Random sequence generation | Allocation concealment | Blinding of participants and personnel | Blinding of outcome assessment | Incomplete outcome data | Selective reporting | Other bias |
|---|---|---|---|---|---|---|---|
| Hartmann et al., (2012) | Unclear | Unclear | High | Unclear | Low | Low | Unclear |
| Jung et al., (2015) | Low | Low | High | Low | Low | Unclear | Unclear |
| Kopf et al., (2014) | Unclear | Unclear | High | Unclear | Low | High | Unclear |
| Miller et al., (2012); | Low | Unclear | High | Unclear | Low | Unclear | Unclear |
| Miller et al., (2014) | Low | Unclear | High | Unclear | Low | Unclear | Unclear |
| Nathan et al., (2017) | Low | Low | High | Low | Low | Low | Unclear |
| Pearson et al., (2018) | Low | Low | Low | Low | Low | Low | Unclear |
| Schroevers et al., (2015) | Low | Unclear | High | Unclear | Low | Unclear | Unclear |
| Tovote et al., (2014) | Low | Unclear | Low | High | Low | High | Unclear |
| van Son et al., (2013) | Low | Low | High | Unclear | Low | Low | Unclear |
| van Son et al., (2014) | Low | Low | High | Unclear | Low | Low | Unclear |