In the present study, we focused on all COGA participants of European ancestry (EA) with genome-wide association (GWAS) data. The analytic sample of the current study varied between two heritable collider variables of interest: tobacco use and educational attainment, described in the measures section below. In our analysis of tobacco use, the total sample size was 7,270, the mean age was 37.67 years (SD = 14.44), and 53% of the sample was female. In our analysis of educational attainment, the total sample size was 7,286, the mean age was 37.69 years (SD = 14.45), and 53% of the sample was female.
