We recently reported an association of a haplotype of tryptophan hydroxylase 2 gene TPH2 with heroin addiction vulnerability in African Americans, as well as a significant association of a genotype pattern of TPH1 and TPH2 variants with heroin addiction in Hispanics (Nielsen et al., 2008a). In the current study, we found that in African Americans, variant rs10506645 in TPH2 was in the top ten of our list of candidate genes. This result supports our previous findings.
