Linkage studies aiming to identify chromosome regions associated with nicotine dependence also have been followed by successful candidate gene studies. Several linkage studies have implicated a region on chromosome 9, which includes genes for the GABAB receptor, in the development of nicotine dependence (Li et al. 2003; Bierut et al. 2004; Gelernter et al. 2004). Based on these linkage analyses, Li (2006) conducted a candidate gene association study of the GABAB2 gene, which lies within the area of chromosome 9 and encodes a component of the GABAB receptor. Several SNPs in this gene were associated with nicotine dependence.
