We conceptualize G–E relationships from an integrated perspective, to mean that genetic and environmental effects come together (in different ways) to contribute to alcohol-related phenotypes4. Three fundamental relationships include: 1) additive effects of genes and the environment; 2) gene-environment correlations; and 3) gene × environment interactions (G×E). An additive relationship is characterized by independent genetic and environmental contributions to an alcohol outcome. Gene-environment correlations and G×E, respectively, describe mediation and moderation relationships in predicting an outcome. A gene-environment correlation identifies a selection effect where genetic vulnerability is associated with exposure to an environment. GxE relationships indicate that genetic vulnerability – or protection – can vary depending on the level of environmental exposure, or, equally, that the effect of the environmental exposure can be different depending on genotype.
