The hope was that studies of G × E, using carefully phenotyped individuals, might yield robust results that could be replicated. Unfortunately, the field has not developed in this way. In the last few years three meta-analyses of the literature have been published, and they reach opposite conclusions: two found no evidence for an interaction [22,23] while one concluded that there was an effect [24]. The view taken by the authors of the positive G × E meta-analysis is that the effect of G × E is broad: “rather than focus on a specific class of studies, we sought to perform a meta-analysis on the entire body of work assessing the relationship between 5-HTTLPR, stress, and depression”. In other words they incorporate more environmental effects and outcomes than envisaged even by the authors of the original study.
