Heat exposure and sauna bathing stimulate the production of brain-derived neurotrophic factor (BDNF), promoting neurogenesis and neuroplasticity.
"So there's it appears that there's the production of all these different kinds of proteins, like BDNF is one that I think has been fairly celebrated as brain-derived neurotrophic factor that seems to maintain neurofunction and, you know, as I understand it, even contribute to neurobiogenesis, so neuroplasticity even later in life." (said at 0:44:29)
The claim is overstated. While acute or controlled passive heating interventions (such as repeated warm-water immersion) have been shown in small human trials to modestly increase circulating peripheral BDNF concentrations, evidence demonstrating that sauna bathing or heat therapy directly stimulates human adult neurogenesis or broad neuroplasticity in the brain is preliminary, indirect, or based on mechanistic extrapolations. Furthermore, excessive or prolonged heat stress has been shown in narrative and preclinical models to activate the hypothalamic-pituitary-adrenal axis and suppress BDNF signaling.
- context: Effects of heat environments on depressive disorders: Neurogenesis-mediated mechanisms. (Journal of thermal biology 2025)
"Heat stress may activate the hypothalamic-pituitary-adrenal (HPA) axis, leading to elevated glucocorticoid levels, which in turn cause hippocampal damage, suppress the expression of brain-derived neurotrophic factor (BDNF), impair neurogenesis and synaptic plasticity, and ultimately promote the onset of depression." (abstract, passage verified)
pubmedfull study (doi) - supports: Seven days of warm-water immersion enhances resting irisin and BDNF, but not klotho, in ol… (Experimental physiology 2026)
"Repeated warm-water immersion increased resting BDNF by 2.43 ng · mL -1 (95% CI: 0.64-4.23; P = 0.005; 1.73-fold) and irisin by 0.94 ng · mL -1 (95% CI: 0.25-1.63; P = 0.005; 1.65-fold)." (abstract, results, passage verified)
pubmedfull study (doi)