The Interplay of Genetics and Neighborhood Context Towards Alcohol Misuse in a Sample of Adult Twins

Introduction: Evidence from twin studies suggests that genetic heritability accounts for a substantial proportion of variance in alcohol misuse. It is plausible that the magnitude of heritability may differ according to environmental factors. Of particular interest is the role of neighborhood context. A growing literature suggests a role of neighborhood characteristics such as neighborhood deprivation on alcohol misuse. Using a co-twin design, this study examines how heritability of alcohol misuse may differ according to neighborhood deprivation.

Method: This cross-sectional study included 2,130 monozygotic and dizygotic same-sex adult twin pairs participating in the Washington State Twin Registry. Alcohol misuse was assessed using the Alcohol Use Disorders Identification Test consumption questionnaire (AUDIT-C). Participant residences were geocoded and linked to Census tract-level sociodemographic measures in order to yield an index for neighborhood deprivation. Taking advantage of the co-twin design, a series of structural equation models was performed with alcohol misuse represented as a latent factor to assess the 1) variance of alcohol misuse explained by additive genetics (A), shared environment (C), and non-shared environment (E); 2) association between neighborhood deprivation and alcohol misuse accounting for confounding due to genetic and shared environment influences on neighborhood selection; and 3) moderation of A, C, and E components on alcohol misuse by neighborhood deprivation. Models were adjusted for age, gender, race, household income, and education level.

Results: A, C, and E components each explained substantial portions of variance in alcohol misuse (A: 37.9%; C: 24.9%; E: 37.2%). Accounting for genetic and shared environmental influences, neighborhood deprivation was significantly associated with higher levels of alcohol misuse (β = .07; p<.001). When examining moderation by neighborhood deprivation, there was marginal evidence that genetic influence on alcohol misuse was weaker at higher compared to lower levels of neighborhood deprivation (interaction-β = -.08; p = .060). Similarly, with increasing levels of neighborhood deprivation the influence of the shared environment was weaker (β = -.18; p <.001). However, the contribution of non-shared environment on alcohol misuse was stronger in neighborhoods with greater deprivation (β = .03; p =.029).

Conclusions: Individuals living in neighborhood environments with greater social deprivation may be more vulnerable to alcohol misuse. Living in more deprived neighborhoods may also potentiate other unique environmental risks for alcohol misuse. However, for those in lower risk neighborhood contexts, genetic and shared environmental factors may have stronger influences.