Association of the dopamine-β-hydroxylase gene with nicotine dependence: No evidence for mediation by personality

We sought to replicate previous studies reporting an association between DBH genotype and smoking behaviour, and extend on this work by including measures of personality as putative mediating variables, in a sample of 141 heavy smokers. Nicotine dependence was measured using the Fagerström Test for Nicotine Dependence; personality was assessed using the Eysenck Personality Questionnaire. All participants were genotyped for the DBH G1368A polymorphism. A oneway ANOVA of nicotine dependence with DBH genotype (GG vs GA + AA) as a between-subjects factor and age as a covariate indicated that individuals with the GG genotype achieved higher nicotine dependence scores than those with the GA and AA genotypes combined (p = 0.036). Of the three dimensions of the Eysenck Personality Questionnaire, nicotine dependence was associated only with psychoticism (p > 0.001). When psychoticism was included as a covariate the association between DBH genotype and nicotine dependence remained significant (p = 0.024). DBH genotype appears to be associated with nicotine dependence. The association we report appears to be independent of age, sex and personality, and both age and psychoticism were independently associated with nicotine dependence. Different phenotype definitions employed by previous studies, such as cigarette consumption rather than nicotine dependence, may explain inconsistency in the published findings.