All individuals in this case/control sample have reported smoking at least 100 cigarettes lifetime, the threshold classically used to define a smoker (Centers for Disease Control and Prevention, 2006). Cases have lifetime FTND scores of 4 or greater, while controls have never exhibited symptoms of dependence (lifetime FTND = 0). This sample therefore is designed to examine the transition from nicotine use to dependence. All subjects (1050 cases and 879 controls) were recruited by two ongoing studies: the Collaborative Genetic Study of Nicotine Dependence (COGEND), a US-based sample (N = 797 cases, N= 813 controls), and the Nicotine Addiction Genetics (NAG) study (Saccone et al., 2007b), an Australian-based sample (N= 253 cases, N= 66 controls). All subjects were self-identified as being of European ancestry. Table I gives demographic details including the distribution of cases and controls, by gender, and mean age and FTND, in the US and Australian samples. The table shows that the mean FTND in cases is very similar across the two recruiting sites (US and Australia), although the proportion of cases and controls recruited differs. Also, the
