Objective: In the present study, we investigated the association between the brain-derived neurotrophic factor (BDNF) Val66Met polymorphism and performance on tests measuring executive functions in a sample of patients with obsessive-compulsive disorder (OCD).
Method: A total of 71 patients diagnosed with OCD by the DSM-IV criteria were included in the study. All patients were assessed using the Yale-Brown Obsessive-Compulsive Scale and the Hamilton Depression Rating Scale. Patients also performed the Wisconsin Card Sorting Test (WCST), the Trail Making Test part A (TMT A) and part B (TMT B), the Tower of London Test (ToL), the Verbal Fluency Test (semantic and lexical şuency) and the Stroop Test. Genomic DNA was extracted from whole blood. The single nucleotide polymorphism (G/A) leading to amino acid substitution at the 66 codon in the BDNF gene (dbSNP number rs6265) was screened by a polymerase chain reaction and restriction digestion analysis in the DNA samples. The performance of the patients on the neuropsychological tests of executive functioning was compared between the patients with Val/Val genotype and Met carriers.
Results: Subjects with Val/Val genotype and Met carriers (Met/Met or Val/Met genotypes) did not differ on socio-demographic and clinical factors, except for the age of onset of the illness, which was earlier in subjects with Val/Val genotype than Met carriers. The performances on the TMT B and TMT B-A, the Stroop Test, and the two measures of the ToL were found to be significantly lower in the Met-allele carriers, compared to the Val/Val group. There were no significant differences in the WCST and the Verbal Fluency Test performances between the two groups.
Conclusions: These findings suggest that the BDNF Met allele may be associated with poorer performance on neuropsychological tests of executive functions in OCD patiens.