From this review of the literature on the influence of genes, environments, and their interaction on cigarette use, we find that significant GxE interactions vary across cigarette use phenotypes. Let us first consider gene-environment interactions contributing to cigarette initiation. Religion was the only environmental variable found to moderate genetic influences on initiation during adolescence (7). More specifically, of the studies investigating gene-environment interaction contributing to initiation (7,95,96,106), only one twin study yielded a significant interaction between aggregated genetic risk and self-rated religiousness (7). The Timberlake et al. (2006) study was the only twin study that included this very specific environmental factor on smoking initiation, even though previous associations have been found between religion and decreased risk for smoking initiation in epidemiological studies. To our knowledge, the interaction between specific genetic variants and self-rated religiousness has not been tested in molecular genetic studies and none of the genetic association studies investigating gene-environment interaction contributing to initiation yielded positive GxE results (9,10). These findings suggest a few different things: either the contribution of genes on initiation remains consistent across different environmental contexts,
