In addition to the above positive findings in EAs, we observed that SNP8^T/T conferred significantly higher risk for CD in the AA family sample, which is consistent with the finding in EA samples. In AA case-control sample, we failed to observe any significant association for SNP3 and SNP8; we also failed to detect a significant role of the interaction between SNP3^G+ and SNP8^T/T on CD in AAs. The decay of linkage disequilibrium caused by more recombination events that have occurred in AAs could underlie this finding (see Figure 1). On the other hand, both the two SNPs showed HWD in cases and HWE in controls suggesting potential associations with CD in AAs too. A SNP8-containing haplotype (constructed from SNP8, SNP7 and a SNP between them) was reported to be associated with polysubstance abuse in AAs in another study (Zhang et al 2004), supporting a role for SNP8 in CD in AAs.
