Most individuals think about genes and environment as two separate and independently acting sets of risk factors. For SUD, this is unlikely to be true. Genetic and environmental risk factors for SUD can correlate, interact or both. We provide detailed definitions below, but here is the short version. Gene-environment correlation arises when genetic and environmental risks are positively inter-related within a population; that is, when people who have high genetic risk are on average also exposed to more environmental risk than average. Gene-environment interaction, by contrast, occurs when the impact of genetic risk factors is moderated by the environment. That is, the same set of genetic factors might have a powerful effect on risk for SUD in one environment and a weak effect in another environment.
