Predicting alcohol consumption in adolescence from alcohol-specific and general externalizing genetic risk factors, key environmental exposures and their interaction.

BACKGROUND: Alcohol consumption is influenced by specific genetic risk factors for alcohol use disorders (AUDs), non-specific genetic risk factors for externalizing behaviors and various environmental experiences. We have limited knowledge of how these risk factors inter-relate through development.
METHOD: Retrospective assessments in 1796 adult male twins using a life history calendar of key environmental exposures and alcohol consumption from early adolescence to mid-adulthood. Analysis by linear mixed models.
RESULTS: The importance of non-specific genetic risk factors on maximal alcohol consumption rose rapidly in early to mid-adolescence, peaked at ages 15-17 years and then declined slowly. Alcohol-specific genetic risk factors increased slowly in influence through mid-adulthood. We detected robust evidence for environmental moderation of genetic effects on alcohol consumption that was more pronounced in early and mid-adolescence than in later periods. Alcohol availability, peer deviance and low prosocial behaviors showing the strongest moderation effects. More interactions with environmental risk factors were seen for the non-specific externalizing disorder risk than for specific genetic risk for AUDs.
CONCLUSIONS: The impact of specific and non-specific genetic influences on alcohol consumption have different development trajectories. Genetic effects on alcohol use are more pronounced when social constraints are minimized (e.g. low prosocial behaviors or parental monitoring) or when the environment permits easy access to alcohol and/or encourages its use (e.g. high alcohol availability or peer deviance). Gene-environment interactions influencing alcohol intake may be more robust at younger ages, indicating greater plasticity of genetic influences early in the development of drinking patterns.