COGEND was designed as a community based case–control study of nicotine dependence. COGEND contains current smokers with nicotine dependence defined by a Fagerstrom Test for Nicotine Dependence (FTND) score ≥ 4 (maximum score of 10) and non-nicotine dependent subjects who had smoked at least 100 cigarettes and had a lifetime FTND score of zero or one. All subjects were ascertained from Detroit and St Louis. Out of the 53,000 subjects who were screened by telephone, 2,800 were interviewed in person and approximately 2,700 donated blood samples for genetic studies23. COGEND contributed 76 individuals with cocaine use disorder (54 nicotine dependent cases based on the FTND, 22 non-dependent smokers) and 1005 individuals without cocaine use disorder (135 nicotine dependent cases based on the FTND, 870 non-dependent smokers).
