Genetic and shared environmental correlations between phenotypes indicate that these latent factors contribute directly not just to one’s own alcohol consumption, but also to affiliation with peers who exhibit particular alcohol-related behaviors. Cruz and colleagues (2012) referred to this process as genetic and environmental selection, though here we have used selection to refer to a distinct process. One implication of this shared liability is that a change in one’s own alcohol use would not necessarily correspond to a change in peers’ alcohol use. In other words, the model suggests that an individual with a genetic liability toward high levels of alcohol consumption is also genetically liable to select peers who drink to excess. Even if one’s own drinking changed in response to an external factor, the genetic liability toward selecting heavy-drinking peers would remain unchanged. This contrasts with the implications of social influence and selection in the form of causal pathways, described below.
