According to another study, heroin dependency is shown to be correlated with a high frequency of allele 36 G>T SNP in the exon 2 of the human KOR gene (hOPRK1), proposing that the T allele might predispose people to addictive behavior or to personality traits at risk for substance abuse (Gerra et al., 2007). The gene discussed is OPRK1; the disease is substance abuse.