The review addressed a clear question and was supported by appropriate inclusion criteria. Although electronic databases and other sources were searched for studies, the restriction to studies written in English coupled with no clear evidence of a systematic search for unpublished studies, meant that relevant studies may have been missed. Suitable methods were employed to minimise the risks of reviewer error and bias for the processes of study selection and study quality assessment, although the authors did not report on whether such methods were used to extract data. Study quality was assessed, but only minimal individual study details were provided, which made it difficult to assess the generalisability of the results. It was unclear which statistical methods the authors used to obtain certain results, since none of the 13 studies had comparator groups. In light of the review's methodological caveats, and the generally poor quality of the included studies, the authors' conclusions are not likely to be reliable.