We have previously reported on univariate estimates for cigarette use in the same sample (Sartor et al., 2015); that study found that while genetic influences made similar contributions in both racial/ethnic groups, EAs and AAs diverged in the extent to which environmental factors shaped their cigarette use. While the influence of familial environmental effects were quite pronounced for EA women in the univariate analysis, non-genetic sources of variance in AA women were almost entirely individual-specific in nature. The current study reveals similar racial/ethnic differences exist for cannabis use; familial environment was somewhat important in EA twins while individual-specific environmental factors dominated in AA pairs.
