In light of the literature supporting the biological and clinical plausibility of CRHR1 involvement in stress reactivity and addiction vulnerability, recent molecular genetic studies have examined the CRHR1 gene for its association with alcoholism, with and without accounting for environmental stress measures (Blomeyer et al., 2008, Chen et al., 2010, Kranzler et al., 2011b, Nelson et al., 2009 Treutlein et al., 2006). As expected, there is more extensive linkage disequilibrium (LD) across CRHRI in Caucasians than in individuals of African ancestry (Bradley et al., 2008, Roy et al., 2012). Additionally, the two populations can be distinguished by a 900 kb inversion polymorphism in those of European descent that is absent in those of African heritage (Stefansson et al., 2005). However in both ethnicities there is a distinct proximal haplotype block (henceforth called haplotype block 1) that spans intron 1 of the gene. Bradley et al (2008) identified a three single nucleotide polymorphism (SNP) haplotype (rs7209436, rs110402, rs242924), commonly known at the TAT haplotype, within this block that was protective against major depression in both African Americans and Caucasians who had
