Two independent authors will perform all screening steps. Title and abstract screening will be conducted with the Mendeley citation management software. The overview authors will screen the titles and abstracts against the eligibility criteria and obtain full reports for all titles that appear to meet the inclusion criteria, or where there is uncertainty. One team of two independent overview authors will manage data in duplicate from each eligible study, using a data collection form in Microsoft Excel, designed specifically to include all the data required. We will only extract data of the included systematic reviews or meta-analyses and not directly from the primary studies, as this process would be beyond the scope of our overview. In cases of disagreement, consensus will be reached with the help of a third author.