Association between polymorphisms of DRD2 and DRD4 and opioid dependence: Evidence from the current studies

Several studies have assessed the association between genetic polymorphisms of DRD2 and DRD4 genes and opioid dependence risk, while the results were inconsistent. We performed a meta‐analysis, including 6,846 opioid dependence cases and 4,187 controls from 22 individual studies, to evaluate the roles of four variants ( DRD2 −141ins/delC, rs1799732; DRD2 311 Ser > Cys, rs1801028; DRD2 ‐related TaqI A, rs1800497 and DRD4 exon III VNTR) in opioid dependence for the first time. We found that the −141delC polymorphism was significantly associated with increased risk of opioid dependence (homozygote comparison: odds ratios [OR], 2.71; 95% confidence interval [CI], 1.74–4.22; dominant comparison: OR, 1.27; 95% CI, 1.09–1.48). Similarly, the TaqI A1 polymorphism was also significantly increased opioid dependence risk (homozygote comparison: OR, 2.06; 95% CI, 1.25–3.42; dominant comparison: OR, 1.34; 95% CI, 1.08–1.67). Moreover, long allele (≥5‐repeat) and 7‐repeat allele of DRD4 exon III VNTR were found to be associated with significantly increased opioid dependence risk (OR, 1.50; 95% CI, 1.24–1.80 and OR, 1.57; 95%, 1.18–2.09, respectively). However, no association was detected between the DRD2 311 Ser > Cys polymorphism and opioid dependence. In conclusion, our results suggested that DRD2 −141ins/delC, DRD2 ‐related TaqI A and DRD4 exon III VNTR polymorphisms might play important roles in the development of opioid dependence. © 2011 Wiley‐Liss, Inc.