What this means

BDNF (brain-derived neurotrophic factor) is a growth factor essential for learning, memory, and the formation of new synapses. The Val66Met variant (rs6265) changes how BDNF is packaged and released in response to neuronal activity. Met carriers release somewhat less BDNF when needed, and some studies link this to small differences in episodic memory performance and stress reactivity. As with COMT, real-world effects are modest and inconsistent across studies — exercise, sleep, and chronic stress all shape BDNF signalling much more than this one letter.

BDNF is a "fertiliser" molecule your brain uses to build new connections — essential for learning, memory, and forming new habits. A common DNA change tweaks how readily BDNF gets released when your neurons are firing. The "Met" version releases a little less of it, and some studies link this to small differences in memory or stress responses. But the effect in real life is tiny. Exercise, sleep, and how much chronic stress you're under shape your BDNF levels far more than which version of this gene you happen to carry.

Caveats

• Replications have been inconsistent, especially in non-European populations.
• Effect sizes on cognition are small in healthy adults.
• Exercise, sleep, and chronic stress affect BDNF signalling much more than genotype.
• This is not a marker for any psychiatric diagnosis.

References

• Egan et al. — The BDNF val66met polymorphism affects activity-dependent secretion of BDNF and human memory and hippocampal function (Cell, 2003)
• Hariri et al. — Brain-derived neurotrophic factor val66met polymorphism affects human memory-related hippocampal activity and predicts memory performance (Journal of Neuroscience, 2003)