We initially identified NrCAM based on convergence between data from genome wide association and studies of drug regulated gene expression [226]. Our initial 1.5 k SNP genome wide association study identified a reproducibly-nominally-positive SNP that was mapped roughly to the region that contained NrCAM as well as other genes. Follow up studies provided confirmatory observations: 11 of 37 tested mid-chromosome seven simple sequence length polymorphisms (SSLPs) display allele frequency differences between abusers and controls in NIDA European- and/or African-American samples that reach nominal significance. Three displayed nominally-significant differences in both populations; fewer than one would have been expected by chance. These nominally-significant results encompassed markers located between 98–103 Mb of chromosome 7.
