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, the effect of GxE in twin studies is quite small, and/or current genetic association studies investigating GxE in cigarette initiation are underpowered to detect effects. Under the first scenario, the environment would have no effect on genetic influences contributing to initiation and encouraging a change in the environment (e.g. increasing self-rated religiousness) would not necessarily reduce cigarette prevalence. The second scenario suggests that the effect of gene-environment interaction is small and certain environments provide only a minimally greater expression of genetic effects. In the context of religiousness, this might be explained by the fact that genetic influences on smoking have been found to be low or nonexistent among individuals raised with a strong religious upbringing (7). The third scenario implies a problem with power, so investigators will need to look towards increasing their sample sizes in future studies of gene-environment interaction in cigarette initiation to detect an effect if it is there.
