Genetic polymorphisms of BDNF on cognitive functions in drug-naive first episode patients with schizophrenia

Brain-derived neurotrophic factor (BDNF) is reported to be involved in cognitive decline in patients with schizophrenia (SZ). Previous studies have found that cognitive deficits remain stable during the chronic disease phase in SZ, but the findings were inconsistent. The role of BDNF in cognitive deficits at different stage of illness remains unclear. This study aimed to examine the effect of BDNF polymorphisms on cognitive deficits in drug-naïve first-episode (DNFE) patients and chronic patients with SZ. 262 DNFE patients, 844 chronic patients, and 1043 healthy controls were recruited to compare 4 polymorphisms in BDNF gene and cognitive function. We found that there was no significant difference in genotype and allele frequencies between SZ patients and controls. However, they were closely related to cognitive functioning. BDNF rs2030324 polymorphism played a strong role in language performance only in DNFE patients with SZ. The language index of DNFE patients with rs2030324 TT and TC genotypes was worse than that of chronic patients, but there was no significant difference in CC genotypes between DNFE and chronic patients. Rs6265 had no significant effect on cognitive functioning in patients and controls. Our result suggests BDNF gene polymorphisms were related to different domains of cognitive function at the different stage of SZ, especially language in DNFE patients.