The present analyses have several strengths and provide an important extension of previous work examining associations between substance use and educational attainment. First, by using twin pairs discordant for substance use/dependence, we were able to control for genetic and environmental confounds that might contribute to the association between substance use and educational attainment. Second, because our participants were in their late 30s when their educational attainment was assessed, we were better able to address lifetime educational attainment than are most previous studies, which have generally focused on high school dropout or educational attainment in 18–25 year-olds whose eventual educational level might not have been reached. Third, we examined educational attainment in a veteran cohort that had access to education via benefits of the G.I. bill, thereby alleviating some of the economic barriers to higher education.
