Genetic marker association with cocaine cue-reactivity. Distributions of SNP genotypes vs. the phenotypes of cocaine cue-reactivity are shown. (A) In GABRA2, the gene for the GABA-A receptor alpha-2 subunit, the G allele of the SNP rs11503014 was associated with high cocaine cue-reactivity, with 11 out of the 12 cue-reactive subjects (right-side “Reactive” pair) having this allele. (B) In OPRM1, the gene for the mu opioid receptor, the A allele of the SNP rs2236256 was associated with non-cocaine cue-reactivity, with 14 of the 18 non-reactive subjects (left-side “Non-Reactive” pair) lacking the A allele.