Polymorphism of the brain-derived neurotrophic factor gene and performance on a cognitive prefrontal test in bipolar patients

Objectives: The aim of the study was to test a possible association between the Val66Met polymorphism of the brain‐derived neurotrophic factor (BDNF) gene and performance on a neurocognitive test, the Wisconsin Card Sorting Test (WCST), in bipolar patients. Methods: Fifty‐four bipolar patients were studied, 18 male and 36 female, aged 18–72 (mean 46 years). The number of perseverative errors (WCST‐P), non‐perseverative errors (WCST‐NP), completed corrected categories (WCST‐CC), conceptual level responses (WCST‐%CONC) and set to the first category (WCST‐1st CAT) were measured in relation to the Val66Met genotypes of BDNF. Results: The percentages of subjects with Val/Val, Val/Met and Met/Met genotypes were respectively 81.5, 16.7 and 1.8%. Subjects with Val/Val and Val/Met genotypes did not differ on clinical factors except for the age of onset of the illness, which was earlier in Val/Val than Val/Met genotype (27 years versus 38 years). The performance in all domains of WCST was significantly better in subjects with Val/Val BDNF genotype compared with Val/Met genotype. Conclusions: The results suggest a role of BDNF in prefrontal cognitive function in bipolar illness. The tests of prefrontal cognition may be considered as endophenotypic markers in bipolar illness.