Table 2 shows the number of individuals in each substance risk group and the prevalence of having completed less than 16 years of education among individuals at varying degrees of risk based on their substance use history. In general, the prevalence of having less than 16 years of education was highest in pairs concordant for the substance risk factor, and decreased through the at-risk members of discordant pairs, to the low-risk members of discordant pairs, to pairs concordant for low-risk. This pattern is consistent with a model in which the likelihood of lower educational attainment increases with increasing substance exposure risk, with one’s own substance use patterns having greater influence than one’s cotwin’s substance use.
