(e.g. selection) (76). Added to this, cigarette use initiation is more likely to occur in schools with higher smoking rates (77), since smoking may seem more normative and acceptable (78) and more social sources of cigarettes may exist (79). This might explain why, despite legislation that prohibits tobacco sales to minors, adolescents are still able to acquire cigarettes through direct purchase from others or from older friends (80). It is also unclear to what extent this is pure environment, rather than active gene-environment correlation whereby individuals are acting on their propensity to use cigarettes by seeking out friend groups that permit cigarette use. Longitudinal study designs of adolescents and their peer groups may help to determine whether gene-environment correlation is present, while disentangling whether socialization or selection has a stronger impact on trajectories of cigarette use. Findings from these longitudinal studies may be helpful in the design of interventions. For example, interventions may want to focus on cognitive factors as a means to mitigate effects of peer group influences on cigarette use through social skills or altering social norms (70).
