Evidence check: BDNF in the context of Stress

BDNF (Brain-Derived Neurotrophic Factor) is a key protein for neuronal plasticity and stress resilience. Chronic stress reduces BDNF expression in the hippocampus, which is linked to increased vulnerability to anxiety and depression. Evidence comes from animal and human studies, but the translation to individual genetic tests is limited. The common polymorphism rs6265 (Val66Met) affects BDNF secretion and is associated with altered stress processing, but effect sizes are small and population-dependent. A direct causal test for 'stress' from a cheek swab is not valid; environmental factors, lifestyle, and epigenetic modifications play a much larger role. The evidence level is moderate: robust associations exist, but insufficient for individual prediction. Caution is warranted against overinterpretation by direct-to-consumer tests that often include BDNF markers without clinical validation.