Moreover, screenings of single-nucleotide polymorphisms (SNPs) in 130 candidate genes incriminated in heroin addiction have recently identified GRIN2A as the most significant candidate, and significantly more C-A-T (rs4587976-rs1071502-rs1366076) haplotypes were found in African American heroin-addicted patients [4]. Here, GRIN2A is linked to heroin dependence.