Persistence of cigarette smoking: familial liability and the role of nicotine dependence

Aims It has been suggested that high genetic vulnerability may explain why smoking persists in spite of general acceptance of the health risks of cigarette smoking. Indeed, heritability estimates for smoking persistence range from 27% to 70%. It has also been suggested that genetic influences on smoking persistence may operate through nicotine dependence, which epidemiological studies have found to be an important risk factor for smoking persistence. We examined alternative ways that familial liability to persistence, nicotine dependence and smoking persistence may be related. Design Cohort study. Setting South-east Michigan, United States. Participants A subset of 389 daily smokers informative for familial smoking characteristics from an epidemiological sample of young adults 26-35 years old (n = 979). Measurements Nicotine dependence criteria were assessed using the NIMH-DIS revised interview and diagnosed according to the DSM-III-R. Familial smoking characteristics were assessed by subject report. Findings Absent nicotine dependence, daily smokers with medium and high familial density of persistence were at increased risk of smoking persistence (OR = 4.2 and 7.0, respectively). However, familial density of persistence was not associated with smoking persistence among nicotine dependent daily smokers. Level of education also appeared to limit the influence of familial liability, although nicotine dependence also modified this effect. Conclusions Nicotine dependence does not appear to be in the causal pathway from familial liability to smoking persistence, but rather modifies the association between them.