The authors conducted a very good search of the literature. The authors searched several electronic databases and the reference lists of articles for additional studies. The search was not restricted to English language studies, but relevant studies could have been missed since unpublished data and abstracts were not used.
The inclusion criteria were stated. The authors made a quality review of the included studies and stated the criteria and their process for the quality review. However, there was no discussion of how judgements were made about the relevance of the included studies, or how the data extraction was performed.
The studies were combined and reported as effect sizes for one of the interventions. It was not, however, possible to combine the studies for the other two interventions because of heterogeneity between the studies. This has led to a narrative account for those interventions, rather than a statistical analysis.
The authors' conclusions follow from the data presented but should be viewed with caution. This is because of limitations in the quality of the studies included in the review, and the lack of statistical analysis on account of there being data missing from the original studies.