Subjects were recruited through the Collaborative Genetic Study of Nicotine Dependence and the Genetic Study of Nicotine Dependence in African Americans.9,17 Institutional Review Board approval was obtained at each institution and written informed consent was obtained from all subjects. Community-based recruitment enrolled subjects aged 25-45 years old. All subjects underwent comprehensive phenotypic assessments of smoking behaviors, including the Fagerström Test for Nicotine Dependence (FTND).18 Nicotine dependent cases were required to be current smokers and have an FTND score of 4 or higher. Non-dependent controls had smoked at least 100 cigarettes (to ensure exposure to nicotine), but had a lifetime maximum FTND score of 1 (Table 1).
