In another approach, we examined 240 genes that may play a role in the vulnerability to develop addiction (Nielsen et al., 2008b). On the 100K GeneChip, 2,081 variants were within 100,000 nucleotides of 167 of these genes (see Supplementary Material, Table S1). We also examined 153 other genes from a list of the Gershon laboratory (Hattori et al., 2005). One thousand one hundred fifty-nine variants are within 100,000 nucleotides of 111 of these genes (see Supplementary Material, Table S2). Of these, ten variants with the smallest P values in each of the two ethnic groups examined (Caucasian and African American) are listed in Table 5. In Caucasians, the variant with the smallest point-wise P value was in the second intron of the metabotropic glutamate receptor 8 gene GRM8 (point-wise P = 0.0003). The variant with the second smallest P value was 44,000 nucleotides upstream of the neural cell adhesion molecule 1 NCAM1 (point-wise P = 0.0003) (Table 5A). In the African American group, the variant with the smallest P value was in the gene encoding the cAMP-specific phosphodiesterase 4B PDE4B
