Genome wide association using denser and denser single nucleotide polymorphism (SNP) sets has allowed identification of a number of genes that display SNPs whose allelic frequencies distinguish individuals with substance dependence from control individuals (Johnson et al., 2006; Liu et al., 2005a,b; Uhl, Liu, Walther, Hess, & Naiman, 2001). rs1395475, an SNP whose allele frequencies distinguished dependent from control individuals, lies at the locus for the PPP3CA gene (Liu et al., 2005a,b) that encodes the alpha catalytic subunit of a Ca2+/calmodulin(CaM)-dependent serine/threonine phosphatase, also called calcineurin or PP2B.
