not support replication of the original finding. Risch et al.23 obtained individual level data from 10 previously published studies (N= 14 250) that met inclusion criteria and analyzed the data using a common model based on number of stressful life events. This re-analysis found no evidence for either a main effect or interaction effect of 5-HTTLPR on depression. Karg et al.25 (56 studies, N= 40 749) and Sharpley et al.26 (81 studies, N= 54 996) both performed literature-based meta-analyses and reported strong evidence for the interaction. Karg et al. and Sharpley et al. criticized the previous analyses of Munafò et al. and Risch et al. for being too restrictive in their inclusion of studies. The approaches of Karg et al. and Sharpley et al., in turn, have been criticized for combining p-values too broadly by allowing studies with an opposite direction of effect to supply supportive evidence, by including results from studies with incompatible statistical and genetic models, and by including outcomes other than depression.22 One key issue contributing to disputes over the appropriateness of the prior reports and meta-analyses is the heterogeneity of the studies.22 Heterogeneity pervades many key factors in the prior analyses, including measurements of depression and
