The linkage region on chromosome 2 at 184 cM has been previously identified as harboring a susceptibility locus for nicotine dependence (Loukola et al., 2008; Straub et al., 1999). The first study reported a linkage signal approximately 35 megabases centromeric, and the second study reported a linkage signal approximately 32 megabases telomeric of the peak reported in this study. In addition, a locus on the short arm of chromosome 2 at 85 cM, which contains NRXN1, has been previously linked to both nicotine and alcohol dependence (Bierut et al., 2007; Nussbaum et al., 2008; Yang et al., 2005), but this locus is approximately 100 megabases from the locus identified in the present study.
