The review question was clearly stated and inclusion criteria specified for participants, intervention and study design. Several relevant sources were searched and attempts were made to minimise publication and language bias. Methods used to select studies, assess validity and extract data were not described, so it is not known whether efforts were made to reduce reviewer errors and bias. Study validity was assessed and results were reported and taken into account when drawing conclusions.
Methods used for several of the main analyses appeared questionable, since means of effect sizes from different scales within the same trial were used in the meta-analyses. Conducting analyses which did not use equivalent interventions also appeared questionable. Although the authors did subsequently run analyses to exclude other factors, these results were not highlighted as likely to be the most reliable and appropriate.
The authors’ cautious conclusions appeared to reflect the limited evidence, but a lack of reporting of review methods plus questionable methods for data synthesis, mean that they should be interpreted with a degree of caution.