In our male sample, we sought to compare the genetic and environmental influences on cigarette use and snus use, as well as on ND as associated separately with these two different tobacco products. The heritabilities of regular snus use and regular cigarette use are similar; however, snus-based ND is more highly heritable, and the relationship between regular snus use and ND (i.e. the β path) is stronger than that between regular smoking and ND. Accordingly, relative to regular smoking and cigarette-based ND, far more of the total genetic variance of snus-based ND is shared with regular snus use (20% v. 57%, respectively). Furthermore, although the differences are modest, it is worth noting that the genetic correlation between MD and RUS (ra = 0.22) is higher than between MD and RUC (ra = 0.13), indicating that the genetic liability shared between MD and tobacco use is higher for this less common method of tobacco administration than for cigarette smoking.
