Participants’ self-reported age, educational attainment, and household income, as well as sex recorded as observed by the interviewer, were included as covariates, given their demonstrated associations with alcohol use (Collins, 2016; Grant et al., 2015). Participants reported their highest level of education by responding to the question “What is the highest grade in school you completed?” Scores were converted to the number of years typically required to complete that level of education and ranged from 0 to 17 years. Participants also reported on their current household gross income based on a 9-point scale ranging from 0 (none) to 9 ($150,000 or more per year). Given the wide range of age in our sample, we created an age group variable to classify participants into three groups: emerging adulthood (ages 18–29, n = 1,068 EA and n = 390 AA), young adulthood (ages 30–44, n = 1,772 EA and n = 626 AA), and middle adulthood (ages 45–65, n = 1,234 EA and n = 275 AA). These age groups are consistent with studies in the epidemiology literature (e.g., Grant et al., 2015). This allowed us to examine similarities and differences in genetic and environmental influences across developmental periods.
