Genes, environments, and interactions: Specifying influences on alcohol use and related phenotypes

Behavior genetics has traditionally involved the partitioning of variance in behavior into latent sources of genetic and environmental influence. Results of that technique proved pivotal in raising awareness of the importance of genes at a time when environmental theories of behavior dominated. With widespread recognition that both genetic and environmental influences are important in the development of virtually all behavior, the new challenge is to move beyond latent sources of variance and to specify the genes and environments involved. This thesis has incorporated strategies from quantitative and molecular genetics to specify genes and environments involved in alcohol use and abuse, and to assess how these genes and environments act and interact. Using data from population-based, Finnish twin studies, a series of quantitative genetic analyses consecutively explore the influence of different environmental variables: socio-regional environment, home environment, and peer influences. Each of these environmental variables also illustrates a different way that the environment can interact with genetic factors. Socio-regional factors moderate influences on alcohol use, with the importance of genetic and environmental influences varying more than fivefold between environmental extremes. Parental monitoring and home atmosphere contribute additively to adolescent behavior problems, while peers' alcohol use exhibits a more complex, interactive relationship with self-reported adolescent alcohol use. A final chapter explores molecular analyses aimed at specifying genes involved in an alcohol-related phenotype. Thus, in a series of consecutive chapters, this dissertation explores (1) environments involved in alcohol use and abuse, (2) the manner in which these environments act and interact with genetic predispositions, and (3) genes involved in alcohol use and abuse.