ADDITIONAL EVIDENCE FOR AN ASSOCIATION BETWEEN THE DOPAMINE-D4 RECEPTOR (D4DR) EXON-III 7-REPEAT ALLELE AND SUBSTANCE-ABUSE IN OPIOID DEPENDENT SUBJECTS - RELATIONSHIP OF TREATMENT RETENTION TO GENOTYPE AND PERSONALITY

The long form of the dopamine D4 receptor (D4DR) exon III repeat polym orphism has been linked in some but not all studies to impulsive, extr avagant and novelty-seeking personality traits that are prominent in a ffiliated behaviours such as attention deficit disorder and substance abuse. In particular, we have reported previously an increased frequen cy of the long seven-repeat D4DR exon III allele in a group of 141 opi oid-dependent subjects compared to 110 control subjects. In order to f urther substantiate the role of D4DR in contributing to heroin addicti on we have genotyped an additional, smaller cohort of opioid-dependent subjects. In this new group of 57 opioid-dependent subjects compared to an expanded group of 143 control subjects a significant difference was observed in overall genotype frequency (p = 0.04). An excess of th e seven-repeat allele of the D4DR receptor gene was also observed comp ared to control subjects (p = 0.06). The frequency of the seven-repeat allele is 15.8% in the heroin addict population vs. 8.1% in the contr ol group, conferring a relative risk of 2.07 (95% CI: 0.98-4.38). An a ssociation between two polymorphisms considered together (D4DR and dop amine D3 receptor) and treatment retention teas observed (p = 0.02). I n a subgroup of 38 opioid-dependent subjects, who were successfully ad ministered the TPQ, higher Harm Avoidance (p < 0. 001) and Novelty See king (NS3; extravagant vs. reserved, p < 0.001) scores were found. In contrast to some previous reports, no relationship was apparent betwee n TPQ scores and treatment retention in this small group of opioid-dep endent subjects.