Objective: To examine the association between genetic variability of IL-1B, which encodes for the proinflammatory cytokine IL-1beta and the risk of developing opioid dependence. To confirm a previous study, we also examined the association between the IL-1B genetic polymorphism and alcohol dependence.

Methods: Genomic DNA was isolated from 60 opioid-dependent, 99 alcohol-dependent patients and 60 healthy nondependent controls. Polymerase chain reaction and restriction fragment length polymorphism were used to determine the presence of single nucleotide polymorphisms at positions -511, -31 and 3954 of IL-1B.

Results: IL-1B -511C and -31T alleles were more frequent in both the opioid-dependent and alcohol-dependent patients compared with the control group: odds ratio (OR, 95% confidence interval) P values corrected for false discovery rate=1.91 (1.14-3.20), P=0.043 and 1.89 (1.19-2.99), P=0.014, respectively, for IL-1B -511C>T; and OR=1.74 (1.02-2.97), P=0.066 and 1.80 (1.13-2.88), P=0.017, respectively, for IL-1B -31T>C. In contrast, no association was observed between opioid dependence and the IL-1B 3954C>T single nucleotide polymorphism [OR=1.60 (0.84-3.02), P=0.15].

Conclusion: This study confirms the previous finding that IL-1B polymorphism is associated with altered risk of alcohol dependence. IL-1B single nucleotide polymorphisms at position -511 and -31, which increase IL-1beta production, occur at a higher frequency in opioid-dependent populations and may be associated, albeit weakly, with an increased risk of opioid dependence.