Association study of brain-derived neurotrophic factor gene polymorphism and alcoholism

Objective: Brain-derived neurotrophic factor (BDNF) influences dopamine and serotonin neurotransmitters that are heavily linked to addiction. A quantitative trait loci study indicated that genes localized to 11p13, where the BDNF gene is mapped (11p13-15), increase the risk for severe alcohol withdrawal. Moreover, a recent study using a pooled-sample microarray suggested that the BDNF gene locus was included in the loci that were shown to be associated with drug abuse. These lines of evidence suggested that BDNF might play some role in the development of or vulnerability to alcoholism and/or clinical characteristics of alcoholic individuals. Methods: The alcoholic subjects consisted of 377 male Japanese patients. A structured interview was used to obtain social background, drinking history, history of violence while intoxicated, history of alcohol withdrawal, and family history of alcoholism. The control group consisted of 336 nonalcoholic male subjects. Genotyping of the G196A polymorphism of the BDNF gene was done by polymerase chain reaction (PCR)-restriction fragment length polymorphism method. Results: Genotype and allele distributions of the BDNF gene polymorphism did not differ significantly between alcoholic and control subjects. However, comparing clinical characteristics across G196A genotypes, we found that alcoholic subjects with violent tendencies and a history of delirium tremens had a significantly higher frequency of AA genotypes and A allele frequencies than those without them. Moreover, alcoholic subjects with the A allele had earlier onset of the disease than those without it. Conclusions: These results indicate that BDNF gene polymorphism might modify phenotypes of alcoholism.