BDNF Val66Met polymorphism and memory performance in older adults: the Met carrier effect is more complex than previously thought.

Brain-derived neurotrophic factor (BDNF) is an important nerve growth factor linked with development and neural plasticity. The Val66Met polymorphism in the BDNF gene has been associated with a significant impact on episodic memory in adults. Azeredo et al.1 investigated effects of the BDNF Val66Met polymorphism on memory performance. Their conclusion was that, in a sample of elderly adults, BDNF Met allele carriers had impaired episodic memory performance as compared to Val/Val homozygotes.1 However, conflicting evidence to this report exists, and the correlation between memory and Met allele carrier status is quite complex. One previous report focusing on older adults suggested that the BDNF Met allele is associated with higher memory performance,2 whereas other studies found no effect of BDNF Val66Met variant on memory in older3 or young adults.4 It is important to note that the effects of the Val66Met polymorphism are due to modification of BDNF synthesis. Azeredo et al. measured BDNF genotype, but not BDNF concentrations. Interestingly, Val66Met polymorphism has been shown to be associated with increased BDNF levels by Zhang et al.,5 vs. the BDNF reduction presumed by Azeredo et al., where aging-related memory decline is possibly explained by reduced neurotrophin synthesis. Another limitation of this study was the failure to exclude psychiatric patients.1 The BDNF increase noted in the study by Zhang et al. was demonstrated in patients with posttraumatic stress disorder, a condition known to have significant impact on memory.

In conclusion, we believe further research into the impact of BDNF genotype on memory should include measurement of BDNF levels as well as psychiatric screening for conditions likely to impact memory function.

Disclosure

The authors report no conflicts of interest.