Fig. 2

Risk of bias summary. Review authors’ judgments about each risk of bias item for each included trial. A green plus sign (+) indicates that there is no substantial concern for bias in the particular quality item. A question mark (?) indicates that conclusions are unable to be drawn regarding potential bias. A red minus sign (−) indicates that there is an explicit concern regarding bias. In the Sadeghpour trial, the dropout rate was very high (42%), justifying the minus sign [1]. The reference numbers to the trials are shown in Table 1