Twin, adoption, and other genetically informative studies designed to disentangle genetic factors from those of the social environment, suggest that heritable effects upon adolescent alcohol use may be both magnified and attenuated by environmental factors (Dick, 2011; van der Zwaluw, 2009). Generally, in less constrained (Dick, 2011), or more adverse environments, such as when the alcohol use of family members and peers is high (Hicks, et al., 2009), variance attributable to genetic influences upon adolescent alcohol use and other externalizing behaviors increases. There is also evidence that environmental moderation may modulate the magnitude of the influence of specific measured genetic polymorphisms upon alcohol use. For instance, one study found a polymorphism in the dopamine transporter gene DAT1 to be associated with serious alcohol problems only among young men who also had alcoholic fathers (Vaske, et al., 2009).
