Preferred Reporting Items for Systematic Reviews and Meta-Analyses

The number of systematic reviews in the literature has increased substantially to include “umbrella reviews” (Conn & Coon Sells, 2014) and systematic reviews of systematic reviews (Adam, Bond, & Murchie, 2015; Corry, While, Neenan, & Smith, 2015). The overall goal of a systematic review is to synthesize and appraise all relevant high-quality research in an effort to answer a specific research or clinical question.