Brain-derived neurotrophic factor gene Val66Met polymorphism and cognitive function in obsessive-compulsive disorder.

In the present study, we have tested the hypothesis that brain-derived neurotrophic factor (BDNF) gene Val66Met polymorphism is associated with obsessive-compulsive disorder (OCD) and also investigated the association between the BDNF Val66Met polymorphism and the performance on tests measuring executive functions in a sample of patients with OCD. A total of 100 patients diagnosed with OCD according to DSM-IV criteria and 110 control subjects were included in this study. Single nucleotide polymorphism (G/A) leading to Val to Met substitution at codon 66 in BDNF was screened in the DNA samples of all participants. The genotype frequencies of BDNF Val66Met polymorphism were compared in OCD patients and healthy controls. The four subgroups of OCD and healthy control subjects, determined according to being Val homozygous or carrying a Met allele, were also compared according to their performance in a battery of neuropsychological tests of executive functions and verbal memory. There was no significant difference for the allele and genotype distributions of BDNF Val66Met polymorphism between the OCD and healthy control groups. Compared to the other three subgroups, OCD-Met carriers were slower on Trail-Making Test part A (TMT A), part B (TMT B) score and its speed-corrected score (TMT B-A). OCD-Met carriers had also poor performance on verbal fluency tasks and several CVLT measures compared only to the healthy control-Met carriers. These results demonstrate that the BDNF Val66Met polymorphism does not appear to be a risk factor for OCD. However, the presence of a BDNF Met allele, which is a known attenuator of BDNF activity, may be associated with a poorer executive functioning in OCD.