Hou et al. [64] investigated the association between the rs1800497polymorphism and heroin dependence. They recruited 530 Han Chinese heroin-addicted individuals from a Methadone Maintenance Treatment (MMT) Program and evaluated their allele and genotype frequencies at the A1 allele [64]. Compared to the allele frequencies in 500 control subjects, the frequency of the A1 allele was significantly higher in MMT patients (P=0.02) and the patients carrying at least one copy of the A1 allele demonstrated mean daily heroin consumption twice as high as patients without the A1 allele (P=0.003) [64]. This study provides evidence for an association between rs1800497 A1 variant and higher mean daily heroin consumption.
