Association between the BDNF Val66Met Polymorphism and Chronicity of Depression

OBJECTIVE: Both clinical and biological factors influence the course of depressive disorders. This study tested for associations between the brain-derived neurotrophic factor (BDNF) gene at the Val66Met locus and the course of major depressive disorder (MDD). METHODS: Three hundred ten Korean subjects (209 patients, 101 controls) were genotyped for rs6265 at nucleotide 196 (G/A), which produces an amino acid substitution at codon 66 (Val66Met) of the gene for BDNF. Course of illness was evaluated both by chronicity of current episode (episode duration >24 months) and by the lifetime history of recurrences. RESULTS: Patients with the Met/Met BDNF genotype had a significantly higher rate of chronic depression than all others. There was a significant dose effect of the Met allele on chronicity. Compared with the Val/Val genotype, the relative risk of chronicity was 1.67 for the Val/Met genotype, and 2.58 for the Met/Met genotype. Lifetime history of recurrent episodes was not related to BDNF genotypes but was significantly associated with younger age of onset and with a history of depression in first degree relatives. CONCLUSION: BDNF genotyping may be informative for anticipating chronicity in major depression.