Although it is clear from the literature that genes influence cigarette use, the motivation to begin smoking is also strongly impacted by the social environment, especially during adolescence (43). As twin and family studies have demonstrated, shared environmental factors also account for a replicable proportion of the variation in initiation specifically (16), and smoking behaviors more generally (44). Thus, research on genetics and cigarette use should take into account social and environmental factors that may modify genetic risk, especially when we consider cigarette use as a dynamic process in which individuals can move from initiation, to intermittent use, to regular use, and/or dependence. Understanding the genetic and environmental factors that interrupt progress along this trajectory or potentiate continued use could be useful for intervening with cigarette use and promoting either prevention of initiation or cessation after continued cigarette use (45). Below, we review epidemiological findings of key environmental covariates that may influence cigarette use and should be considered for genetic research on cigarette use.
