In summary, these results indicate that the covariation between one’s alcohol consumption and the drinking behaviors of one’s peers is the result of a complex combination of genetic and environmental influences, some of which are shared directly, while others operate in a causal fashion. Molecular genetic studies could be designed to identify specific genetic variants underlying these processes, though as with any complex trait, genetic effect sizes are likely to be quite small, and are potentially susceptible to moderation by other variants and by environmental factors. Perhaps more plausibly, potential environmental risk factors – e.g., parental monitoring or neighborhood characteristics (Chuang et al., 2005) – could be explicitly included in a model to determine the extent to which they influence alcohol related outcomes.
