Evidence check: BDNF in the context of fatigue

BDNF (Brain-Derived Neurotrophic Factor) is crucial for neuronal survival and plasticity. Some studies suggest an association between low BDNF levels and fatigue, especially in conditions like multiple sclerosis or chronic fatigue syndrome. However, the evidence for the general population is weak and not causal. Most data come from observational studies or animal models. A genetic test for BDNF variants (e.g., Val66Met) cannot reliably predict individual fatigue risk, as fatigue is multifactorial (sleep, stress, diet, exercise). Lifestyle factors such as aerobic exercise influence BDNF expression far more than single polymorphisms. Therefore, a standalone genetic assessment without clinical context is misleading. Evidence grade: mechanistic / unclear. No direct safety concerns, but caution against overblown claims from direct-to-consumer tests.