Evidence for an Association between Brain-Derived Neurotrophic Factor Val66Met Gene Polymorphism and General Intellectual Ability in Early-Onset Schizophrenia

Background: Brain-derived neurotrophic factor (BDNF) plays a crucial role in the survival, development and maintenance of neuronal systems, and the Val66Met polymorphism has been implicated in memory functions. Method: We examined the association of BDNF with general intellectual ability in 161 individuals including 53 early-onset patients with schizophrenia (EOS), 91 healthy biological relatives, and 17 relatives with major depressive disorder (MDD), using the Wechsler Intelligence Scales (WISC). Results: Regardless of diagnosis, individuals with the Met66 allele had a significantly higher performance score than those homozygous for Val66 on vocabulary, block design and object assembly subtests of the WISC. EOS probands showed poor performance on all IQ subtests compared with relatives with and without MDD. Limitations: Relatively smaller sample size of individual genotypes. Conclusions: BDNF genotype may play a role in specific cognitive functions and dimensions of intelligence. The Met allele appears to be associated with superior performance in IQ compared with relatives Val/Val genotype