Although the twin studies suggest moderate genetic influences on nicotine dependence, little information is provided about the chromosomal locations harboring susceptibility loci/genes for nicotine dependence. Linkage-based genome-wide scans for smoking behavior have been reported by Straub et al. [4] on the Christchurch sample of New Zealand (130 families with 343 genotyped individuals) and the Richmond sample of Virginia (91 families with 264 genotyped individuals), and by Duggirala et al. [5] and Bergen et al. [6] on the Collaborative Study on the Genetics of Alcoholism data (COGA; 105 families with 987 genotyped individuals). However, only a few susceptibility regions for nicotine dependence from one study were replicated in another study.
