COGEND was designed as a community based case–control family study of nicotine dependence. The COGEND ascertainment protocol identified current smokers with nicotine dependence defined by an FTCD score ≥4 (maximum score of 10); non-nicotine dependent subjects who had smoked at least 100 cigarettes and had a lifetime FTCD score of zero were also recruited. All subjects were ascertained from Detroit and St. Louis. Approximately 53,000 subjects were screened by telephone, 2,800 were personally interviewed, and nearly 2,700 donated blood samples for genetic studies. The COGEND study contributed 275 nicotine dependent cases and 1,082 non-nicotine dependent smoking controls to this nicotine dependence genetic analyses. Of these, 125 nicotine-dependent cases and 706 non-nicotine dependent controls overlap with the samples used in Bierut et al.2007, and Saccone et al.2007(5–6).
