The next cohort, those born in the middle 1930s to the middle to late 1940s, aged into the risk of smoking at a time when cigarettes were cheap and ubiquitous, with regular images of cultural icons smoking. Because these social mechanisms influenced all individuals regardless of genetic makeup, the genetic influences on smoking will start to decrease for this birth cohort. That is, genetic characteristics are less likely to differentiate smokers from nonsmokers. This decrease is consistent with the social push model.
