The claim
“Sauna boosts BDNF and grows your brain.”
Hot air. Two small studies of men found that hot water and a heated suit raised blood BDNF for a short while. The sauna itself hasn't been tested, and we found no study that tied heat to brain growth.
Updated Sep 24, 2026 · 1 study reviewed
Nothing solid supports it, or the best evidence runs against it.
People say it in places like these
Podcasts
Sauna raises BDNF and feeds your brain like fertilizer.
Biohacking blogs
Regular heat exposure grows your brain and protects it from decline.
The research found this
BDNF stands for brain-derived neurotrophic factor, and we found no study that measured it after a sauna. The human studies used other kinds of heat, and each one measured BDNF in the blood.
On one day, eight healthy men sat in water up to the neck for 20 minutes at 42°C, and on another day they did the same at 35°C. After the hot soak, serum BDNF was higher at the end and 15 minutes later, and it was back to its starting level by 30 minutes.Source 1 · Crossover trialHead-out immersion in hot water increases serum BDNF in healthy malesKojima D, Nakamura T, Banno M, et al.. International Journal of Hyperthermia, 2018.Read the paper ↗PubMed ↗ The abstract leaves out how big the rise was.
A second study put ten recreationally active men in a water-perfused suit for 90 minutes. Water flowing through the suit can heat or cool different parts of the body. Heating the whole body raised serum BDNF from 19.1 to 25.9 ng/mL, and plasma BDNF went from 2.74 to 4.58 ng/mL. When the suit heated only the legs and cooled the upper body, BDNF did not rise.Source 2 · Crossover trialSerum and plasma brain-derived neurotrophic factor concentration are elevated by systemic but not local passive heatingOgawa T, Hoekstra SP, Kamijo YI, et al.. PLOS ONE, 2021.Read the paper ↗PubMed ↗ Platelet counts climbed along with BDNF, and each platelet carried the same amount of BDNF as before.
The one long trial also heated only part of the body. Researchers randomly split 60 young adults into four groups: exercise, 45-minute foot baths at 42°C, both, or neither. The sessions ran three times a week for eight weeks, and neither thinking test scores nor plasma BDNF changed.Source 3 · Randomized trialEight weeks of post‐exercise local heating does not improve cognition and plasma brain‐derived neurotrophic factor concentrationsCheng JL, Coombs GB, Pizzola C, et al.. Experimental Physiology, 2025.Read the paper ↗PubMed ↗
Other brain claims for sauna come from long-running Finnish studies of dementia, and the dementia page covers them.
The dial reads 81°H for four reasons
How the reading adds up
22 + 16 + 23 + 20 = 81°H
EvidenceWhat kind of human evidence exists?
22/25The human data come from 8 men soaking in hot water and 10 men wearing a heated suit.Source 1 · Crossover trialHead-out immersion in hot water increases serum BDNF in healthy malesKojima D, Nakamura T, Banno M, et al.. International Journal of Hyperthermia, 2018.Read the paper ↗PubMed ↗Source 2 · Crossover trialSerum and plasma brain-derived neurotrophic factor concentration are elevated by systemic but not local passive heatingOgawa T, Hoekstra SP, Kamijo YI, et al.. PLOS ONE, 2021.Read the paper ↗PubMed ↗ A 60-person trial of foot baths found no change.Source 3 · Randomized trialEight weeks of post‐exercise local heating does not improve cognition and plasma brain‐derived neurotrophic factor concentrationsCheng JL, Coombs GB, Pizzola C, et al.. Experimental Physiology, 2025.Read the paper ↗PubMed ↗
ConsistencyHave other studies found the same thing?
16/25Whole-body heating raised BDNF in both small studies that tried it. Heating only the legs failed to move it in the suit study, and eight weeks of hot foot baths left it unchanged.Source 2 · Crossover trialSerum and plasma brain-derived neurotrophic factor concentration are elevated by systemic but not local passive heatingOgawa T, Hoekstra SP, Kamijo YI, et al.. PLOS ONE, 2021.Read the paper ↗PubMed ↗Source 3 · Randomized trialEight weeks of post‐exercise local heating does not improve cognition and plasma brain‐derived neurotrophic factor concentrationsCheng JL, Coombs GB, Pizzola C, et al.. Experimental Physiology, 2025.Read the paper ↗PubMed ↗
MagnitudeDoes the claim match the size of the effect?
23/25The claim promises a growing brain. After a hot soak, the rise in blood BDNF was gone by 30 minutes.Source 1 · Crossover trialHead-out immersion in hot water increases serum BDNF in healthy malesKojima D, Nakamura T, Banno M, et al.. International Journal of Hyperthermia, 2018.Read the paper ↗PubMed ↗
DoseDoes the studied dose match how people use it?
20/25A sauna routine has yet to be tried. The studies used 20 minutes of neck-deep soaking at 42°C and 90 minutes in a water-perfused suit.Source 1 · Crossover trialHead-out immersion in hot water increases serum BDNF in healthy malesKojima D, Nakamura T, Banno M, et al.. International Journal of Hyperthermia, 2018.Read the paper ↗PubMed ↗Source 2 · Crossover trialSerum and plasma brain-derived neurotrophic factor concentration are elevated by systemic but not local passive heatingOgawa T, Hoekstra SP, Kamijo YI, et al.. PLOS ONE, 2021.Read the paper ↗PubMed ↗
The claim drifts from the data here
The claim jumps from a blood test to the brain, and none of these studies looked at the brain itself. After hot water, the blood rise was gone by 30 minutes, and in the suit study BDNF climbed in step with platelets.Source 1 · Crossover trialHead-out immersion in hot water increases serum BDNF in healthy malesKojima D, Nakamura T, Banno M, et al.. International Journal of Hyperthermia, 2018.Read the paper ↗PubMed ↗Source 2 · Crossover trialSerum and plasma brain-derived neurotrophic factor concentration are elevated by systemic but not local passive heatingOgawa T, Hoekstra SP, Kamijo YI, et al.. PLOS ONE, 2021.Read the paper ↗PubMed ↗
BDNF rose only when the whole body was heated.Source 2 · Crossover trialSerum and plasma brain-derived neurotrophic factor concentration are elevated by systemic but not local passive heatingOgawa T, Hoekstra SP, Kamijo YI, et al.. PLOS ONE, 2021.Read the paper ↗PubMed ↗ A normal sauna warms the body's core less than a long hot soak. When one study compared them directly, three 10-minute sauna rounds raised core temperature 0.4°C, and 45 minutes in 40.5°C water raised it 1.1°C.Source 4 · Crossover trialComparison of thermoregulatory, cardiovascular, and immune responses to different passive heat therapy modalitiesAtencio JK, Reed EL, Wiedenfeld Needham K, et al.. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 2025.Read the paper ↗PubMed ↗
Put it to use
BDNF makes a weak reason to take a sauna for now. If brain health is your goal, the Finnish data on dementia is the better place to start, and that page lays out its limits.
From our sister magazine
Sauna Monthly compares how infrared cabins and hot-rock saunas heat the body
BDNF rose only when the whole body warmed up. Our sister magazine compares the heat of infrared cabins and hot-rock saunas.
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Sauna Monthly compares barrels and cabins that run hot-rock heaters.
People also ask
Does sauna increase BDNF?
It hasn't been tested. In small studies of men, hot water at 42°C and a heated suit raised BDNF in the blood for a short time.Source 1 · Crossover trialHead-out immersion in hot water increases serum BDNF in healthy malesKojima D, Nakamura T, Banno M, et al.. International Journal of Hyperthermia, 2018.Read the paper ↗PubMed ↗Source 2 · Crossover trialSerum and plasma brain-derived neurotrophic factor concentration are elevated by systemic but not local passive heatingOgawa T, Hoekstra SP, Kamijo YI, et al.. PLOS ONE, 2021.Read the paper ↗PubMed ↗
Can heat therapy improve memory or thinking?
In a randomized trial of 60 young adults, eight weeks of hot foot baths three times a week did not improve thinking test scores or plasma BDNF.Source 3 · Randomized trialEight weeks of post‐exercise local heating does not improve cognition and plasma brain‐derived neurotrophic factor concentrationsCheng JL, Coombs GB, Pizzola C, et al.. Experimental Physiology, 2025.Read the paper ↗PubMed ↗
Check these claims next
48°H
Unsettled
“Sauna cuts your risk of dementia by 66%.”
The 66% comes from 8 cases of dementia among about 200 Finnish men who took four to seven saunas a week. A larger Finnish study by a different team found no link in its most frequent bathers. In that study, saunas above 100°C went with more dementia during the first 20 years.
57°H
Unsettled
“Sauna treats depression.”
In a trial of 29 people, one session in a medical heating device eased depression more than a sham session with the main lamps switched off. Real heat did no better than sham heat when a pilot paired talk therapy with an infrared dome.
74°H
Stretched
“Sauna switches on heat shock proteins that slow aging.”
In one sauna study, blood levels of heat shock protein 72 rose 48.7% on average after 30 minutes at 73°C. A review of 51 controlled heating studies found no change overall, and the idea that these proteins slow aging comes from animal research.
We cited these sources
- 01Kojima D, Nakamura T, Banno M, Umemoto Y, Kinoshita T, Ishida Y, et al.. Head-out immersion in hot water increases serum BDNF in healthy males. International Journal of Hyperthermia. 2018;34(6):834-839. doi:10.1080/02656736.2017.1394502 PMID 29157042
- 02Ogawa T, Hoekstra SP, Kamijo YI, Goosey-Tolfrey VL, Walsh JJ, Tajima F. F, et al.. Serum and plasma brain-derived neurotrophic factor concentration are elevated by systemic but not local passive heating. PLOS ONE. 2021;16(12):e0260775. doi:10.1371/journal.pone.0260775 PMID 34882699
- 03Cheng JL, Coombs GB, Pizzola C, Mattook K, Armstrong C, MacDonald MJ, et al.. Eight weeks of post‐exercise local heating does not improve cognition and plasma brain‐derived neurotrophic factor concentrations. Experimental Physiology. 2025:EP092810. doi:10.1113/ep092810 PMID 41389004
- 04Atencio JK, Reed EL, Wiedenfeld Needham K, Lucernoni KM, Comrada LN, Halliwill JR, et al.. Comparison of thermoregulatory, cardiovascular, and immune responses to different passive heat therapy modalities. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology. 2025;329(1):R20-R35. doi:10.1152/ajpregu.00012.2025 PMID 40332494