A three-level meta-analytic model was conducted using the R package metafor . Levels 1,2 and 3 represent the individuals, within-study variances, and between-study variances, respectively . Most articles included in this meta-analysis provided multiple summary statistics; a three-level model allowed for the computation of an overall mean effect size while accounting for between-study and within-study heterogeneity. We reported the overall effect size of the three-level meta-analytic model and the Higgins and Thompson's I 2 , the amount of variation that is not attributed to sampling error, for between-study and within-study heterogeneity variances . An ANOVA was computed to compare two and three-level models to ensure that the model selected provided the best fit for the data. To investigate a potential publication bias, effect sizes were plotted against sample size. Egger's regression was employed where an intercept differing from 0 in this test indicates asymmetry and possible publication bias .