for nicotine dependence in populations of European descent (Figure 3) (113, 139). A comprehensive meta-analysis involving more than 32,000 subjects confirmed the three unique loci in this gene cluster that affect smoking quantity (112). In Asians, a locus tagged by rs578776 overlapped with a locus tagged by rs588765, and variants in this distinctive linkage disequilibrium pattern were reported to influence smoking initiation, smoking cessation (84), and smoking quantity (84, 146).
