The research question was well defined and supported by detailed inclusion criteria. Several electronic databases were searched. Only published studies in English were included, so publication and language bias could not be ruled out. The research process was not reported and so it was unclear whether steps were taken to reduce reviewer error and bias.
Study quality was assessed and the generally poor quality of the studies was taken into consideration in the analysis. A narrative synthesis appeared appropriate considering the diversity of interventions and participant characteristics. The included studies did not include participants with a history of poor adherence, so the findings may not be generalisable to those with established adherence problems.
The authors conclusions are supported by the data presented, but the possibility of language and publication biases and lack of reporting of the review process should be borne in mind.