It is likely that genetic factors and one's social context jointly shape one's risk for smoking behaviors.9, 10, 11 Further, many of the genetic and environmental risk factors are likely to be shared with other substance-use behaviors and disorders.19, 29 Although no study to our knowledge has specifically examined the interaction between genetic variants and neighborhood social cohesion or physical disorder, previous studies have reported interactions between genetic variants and individual-level predictors of substance use, such as the experience of traumatic life events.30, 31 For example, interactions between trauma with genetic variants including dopaminergic and nicotinic receptors have been reported as incurring risk for smoking.32, 33, 34 Evidence for the interaction between the experience of childhood trauma and risk at the 5-HTTLPR locus with regards to smoking behaviors is mixed with both positive35 and negative22, 23 results. Relatedly, interactions have been observed between aggregated, latent genetic and environmental influences on cigarette smoking using the genetically informative twin-family design. Twin studies have demonstrated that the genetic risk for adolescent smoking is higher in urban than rural communities.36, 37 The authors posited
