The methodology followed the guidelines given by Smith, Devane, Begley, and Clarke (2011). The research design was determined a priori. The research questions, search strategy, and inclusion/exclusion criteria were established before the actual search and review. Flow of information through the different phases of this systematic review is presented in Figure 1, as guided by the PRISMA statement (Liberati et al., 2009; Moher, Liberati, Tetzlaff, & Altman, 2009).
Flow diagram of study selection