Education and alcohol use: A study of gene-environment interaction in young adulthood

Abstract

The consequences of heavy alcohol use remain a serious public health problem. Consistent evidence has demonstrated that both genetic and social influences contribute to alcohol use. Research on gene-environment interaction (GxE) has also demonstrated that these social and genetic influences do not act independently. Instead, certain environmental contexts may limit or exacerbate an underlying genetic predisposition. However, much of the work on GxE and alcohol use has focused on adolescence and less is known about the important environmental contexts in young adulthood. Using data from the young adult wave of the Finnish Twin Study, FinnTwin12 (N = 3402), we used biometric twin modeling to test whether education moderated genetic risk for alcohol use as assessed by drinking frequency and intoxication frequency. Education is important because it offers greater access to personal resources and helps determine one's position in the broader stratification system. Results from the twin models show that education did not moderate genetic variance components and that genetic risk was constant across levels of education. Instead, education moderated environmental variance so that under conditions of low education, environmental influences explained more of the variation in alcohol use outcomes. The implications and limitations of these results are discussed.

Keywords: Alcohol use; Education; Gene-environment interaction; Twin models; Young adults.

Figure 1. Extended Univariate and Bivariate GxE Models

Figures show extended univariate model (left) and simplified bivariate model (right) with only the genetic components included for ease of display. Moderation is estimated through the β on each of the a, c, and e paths. In the bivariate case, the moderation can act on both the shared path between the moderator and trait (a₂₁) and the path unique to the trait (a₂₂). In the case when the extended univariate model is selected over the bivariate, all of the shared paths between trait and moderator are collapsed into the means portion of the model (M).

Figure 2. Path Estimates for Intoxication Frequency GxE Models

Figures show path and moderation estimates from full model for intoxication frequency in both females (left) and males (right). Each means portion of the model includes the twin’s education (Edu₁) and the influence of their co-twin’s education (Edu₂).

Figure 3. Change in Variance Components for Intoxication Frequency

Results from GxE models for intoxication frequency. Lines represent changes in raw variance of components across educational attainment (standardized). Only the change in unique environment (E) was significant.

Figure 4. Path Estimates for Drinking Frequency GxE Models

Figures show path and moderation estimates from full model for drinking frequency in both females (left) and males (right). Each means portion of the model includes the twin’s education (Edu₁) and the influence of their co-twin’s education (Edu₂).

Figure 5. Change in Variance Components for Drinking Frequency

Results from GxE model for drinking frequency. Lines represent changes in raw variance of components across educational attainment (standardized). Change in both shared (C) and unique environment (E) was significant.