The claim
“Sauna boosts BDNF and grows your brain.”
Hot air. No study has measured BDNF after a sauna, and we found none linking heat to brain growth. Hot water and a heating suit raised blood BDNF briefly in two small studies of men.
Updated Sep 24, 2026 · 1 study reviewed
Nothing solid supports it, or the evidence points the other way.
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 has measured it after a sauna. The human data come from other kinds of heat, and all of them measured BDNF in blood.
In a crossover study, eight healthy men sat in water up to the neck for 20 minutes at 42°C on one day and at 35°C on another. After the hot soak, serum BDNF was higher at the end and 15 minutes later, and it was back to baseline 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 does not give the size of the rise.
A second study put ten recreationally active men in a water-perfused suit for 90 minutes. Heating the whole body raised serum BDNF from 19.1 to 25.9 ng/mL and plasma BDNF 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 rose along with BDNF, and the amount of BDNF per platelet stayed the same.
The one long trial used foot baths. Sixty young adults were randomized to exercise, 45-minute foot baths at 42°C, both, or neither. The sessions ran three times a week for eight weeks, and neither thinking tests 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 ↗ Local heating had already failed to move BDNF in the suit study.
Brain claims for sauna otherwise lean on Finnish cohort data about dementia, and those have their own page.
The dial reads 81°H for four reasons
How the reading adds up
22 + 16 + 23 + 20 = 81°H
EvidenceWhat kind of evidence exists in people?
22/25The human data come from hot water and water-perfused suits in groups of 8 and 10 men.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 ↗
ConsistencyHas the finding held up?
16/25Whole-body heating raised BDNF in both small studies that tried it. Heating only the legs did nothing in a single session, and eight weeks of hot foot baths left BDNF 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 rise was brief. After a hot soak, serum BDNF was back to baseline by 30 minutes, and we found no study that measured brain growth after heat.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 protocol match how people use it?
20/25No sauna protocol has been tested. The studies used 20 minutes of neck-deep immersion 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. In hot water the rise was gone by 30 minutes, and in the suit study BDNF rose 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 ↗ None of these studies measured the brain.
A normal sauna raises core temperature less than a long hot soak. In a head-to-head test, three 10-minute sauna rounds raised it 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 ↗ 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 ↗
Put it to use
Leave BDNF out of your reasons for a sauna for now. If brain health is the goal, weigh the Finnish cohort data on dementia and read their limits.
From our sister magazine
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People also ask
Does sauna increase BDNF?
Nobody has measured it. Hot water at 42°C and a heated suit raised BDNF in the blood for a short time in small studies of men.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
Early
“Sauna cuts your risk of dementia by 66%.”
The 66% rests on 8 cases of dementia among about 200 Finnish men who took four to seven saunas a week. A larger, independent Finnish cohort found no link in its most frequent bathers, and saunas above 100°C went with more dementia in its first 20 years.
57°H
Early
“Sauna treats depression.”
One session of medical whole-body heating eased depression more than a sham session in a trial of 29 people. When a pilot trial added infrared-dome heat to talk therapy, it did no better than sham heat.
74°H
Stretched
“Sauna switches on heat shock proteins that slow aging.”
One sauna study found blood heat shock protein 72 up 48.7% on average after 30 minutes at 73°C, and a review of 51 controlled heating studies found no change overall. No study in people has tied heat shock proteins from a sauna to slower aging.
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