Chunk #24 — RESULTS — Early conversion to daily smoking and rapid progression to heavy smoking mediated genetic associations with adult smoking problems
We derived an index of adult smoking problems from a principal components analysis of 3 indicators: a) pack-years smoked by age 38 years; b) total number of Fagerstrom symptoms across assessments; and c) the number of assessments at which study members reported cessation failure. The adult smoking problems factor explained 78% of the variance in the 3 indicators. Individuals at higher genetic risk developed more smoking problems in adulthood (r=0.10, p=0.012). We next tested whether this association was accounted for by the more rapid developmental progression of smoking behavior among individuals at higher genetic risk. 81% of this association was accounted for by the two adolescent developmental phenotypes of early conversion to daily smoking and rapid progression to smoking≥20 cigarettes/day (Supplemental Table 4). As a further attempt to address the question of whether preventing rapid progression from smoking initiation to heavy smoking could mitigate genetic risks, we conducted a utopian control analysis:51 We asked whether genetic risks continued to predict adult smoking problems in the subset of individuals who did initiate smoking, but who did not exhibit either of the
