The long history of inconsistent reports could reflect more complicated genetic substrates than have heretofore been recognized. In two recent studies, we (Gelernter et al., 2006; Yang et al., 2007) found a broader genomic region on chromosome 11q23, including a gene cluster of NCAM1, TTC12, ANKK1 and DRD2 (“NTAD” cluster), spanning ~542 kb, to be associated with the genetic risk of nicotine dependence (ND) and alcohol dependence (AD), respectively.
