Sauna for major depressive disorder
Evidence review
Overview
Whole-body hyperthermia (raising core temperature to about 101.3 F) and hyperthermic baths have produced rapid reductions in depressive symptoms in some small randomized trials of adults with major depressive disorder. The best-controlled trial used a single session against a credible sham and found a HAM-D advantage that persisted for 6 weeks; secondary analyses of that trial linked response to an acute rise in interleukin-6 (Flux 2023, PMID 37085494; Mac Giollabhui 2024, PMID 38677624). The hot-water bath trials are weaker than they first appear: the sham-controlled trial was significant only with one-sided testing, and the trial against exercise was open label, with its 2-week benefit not significant per protocol or at 8 weeks. A 2025 randomized trial in which both arms also received CBT found large improvements in both the active and sham arms with no added benefit detectable, and a 2019 systematic review of 7 small studies judged the evidence insufficient for general recommendations. Evidence is limited to short follow-up, small samples and mostly medication-free or adjunctive settings. In two analyses of the Japanese JAGES cohort of older adults, daily home tub bathing was associated with fewer new cases of depressive symptoms over 3 and 6 years, significantly in winter; these are associations with screening-scale scores, not trials in diagnosed depression.
Key findings
- Single WBH session vs sham: HAM-D difference -6.53 (95% CI -9.90 to -3.16) at week 1 and -4.27 (-7.94 to -0.61) at week 6 (Janssen 2016, n=29 analyzed)
- Hyperthermic baths 104 F twice weekly vs sham: HAM-D difference 3.14 points at 2 weeks, P=.037 one-sided (Cohen d 0.62, 95% CI -0.05 to 1.29); not significant 4 weeks after treatment (Naumann 2017, n=36)
- Hyperthermic baths vs exercise, open label: HAM-D difference 4.3 points at 2 weeks (95% CI 2.16 to 6.42, ITT); per protocol 2.7 (95% CI -0.22 to 5.69) and at 8 weeks 2.9 (95% CI -0.40 to 6.14), both not significant (Naumann 2020, n=45)
- CBT + WBH vs CBT + sham WBH: BDI-II fell -19.07 vs -21.10; no advantage for active heat (Mason 2025, n=30)
- Systematic review, 7 studies, 148 participants: 19 of 21 mood end-points showed effect sizes d >= 0.8, largest with target core temperatures of 100.4-102.2 F; evidence judged insufficient for general recommendations (Hanusch 2019)
- JAGES cohort, older adults without depression: daily vs less frequent winter tub bathing, IRR 0.77 (95% CI 0.65-0.91) for incident depressive symptoms over 3 years (Yagi 2019, n=4,466) and OR 0.76 (0.59-0.98) over 6 years (Hayasaka 2024, n=6,452); summer estimates were not significant.
Every study we reviewed
7 found benefit · 2 found no effect
Each study was checked on PubMed. The colored edge shows the direction of the result. The research library lists 36 studies on depression, across all heat and cold therapies, including case reports and older work not graded here.
Whole-Body Hyperthermia for the Treatment of Major Depressive Disorder: A Randomized Clinical Trial.
Janssen CW et al. JAMA Psychiatry. 2016. PubMed 27172277 · DOI · Free full text
- Who
- medically healthy, psychotropic-free adults 18-65 with MDD, HAM-D-17 >= 16
- What
- single session of whole-body hyperthermia vs sham of matched length without intense heat
- Protocol
- 101.3 core (target) °F · mean 107 heating (range 81-140) + 60 cool-down min · single session/wk
- Measured
- HAM-D-17 over 6 weeks
- Result
- WBH vs sham HAM-D: week 1 -6.53 (95% CI -9.90 to -3.16, P<.001); week 2 -6.35 (-9.95 to -2.74, P=.001); week 4 -4.50 (-8.17 to -0.84, P=.02); week 6 -4.27 (-7.94 to -0.61, P=.02). 34 randomized, 30 treated, 29 in modified ITT (week 6: 15 WBH, 11 sham). Overall adverse events did not differ between groups; headache, fatigue and dry mouth were most common, with numerically more sweating and nausea after WBH.
- Limitations
- Single session; small sample with 4 sham-arm dropouts by week 6; medication-free, medically healthy participants; outcome assessors blinded, but 71.4% of the sham group believed they received WBH; not yet replicated with the same design; full text read from a publisher extract.
A Randomized Trial Testing a Novel Mind and Body Intervention for Depression: Cognitive Behavioral Therapy (CBT) and Whole-Body Hyperthermia (WBH).
Mason AE et al. Glob Adv Integr Med Health. 2025. PubMed 41146956 · DOI · Free full text
- Who
- adults with MDD, all receiving CBT
- What
- CBT plus WBH in an infrared sauna device vs CBT plus sham WBH
- Protocol
- about 135 ambient; 101.3 core (target) °F · mean 98.5 (sham 74.9) min · 4 WBH sessions every other week/wk · 8 wk
- Measured
- acceptability (primary); BDI-II change (secondary)
- Result
- BDI-II change -19.07 (SE 2.69) in WBH arm vs -21.10 (SE 2.41) in sham arm, both P<0.0001 within-arm; 80.0% vs 92.9% no longer met DSM-5 criteria. No advantage for active WBH. No serious adverse events; in the WBH arm headache was reported 28 times by 13 participants, lightheadedness 15 times by 7 and nausea 8 times by 5; 29 of 30 completed the final assessment.
- Limitations
- Primary outcome was acceptability, not powered for efficacy; single-blind, and every active-arm participant correctly guessed allocation; sham involved about 75 min of warm exposure and may not have been inert; CBT in both arms; 3 of 15 WBH participants never reached target temperature.
Feasibility and acceptability of an integrated mind-body intervention for depression: whole-body hyperthermia (WBH) and cognitive behavioral therapy (CBT).
Mason AE et al. Int J Hyperthermia. 2024. PubMed 38743265 · DOI · Free full text
- Who
- adults with MDD
- What
- single-arm CBT plus WBH (8 weekly sessions, later reduced to 4 every other week)
- Protocol
- about 135 ambient; 101.3 core (target) °F · up to 110, later up to 140, heating min · 1 (later every other week)/wk · 8 wk
- Measured
- feasibility; BDI-II change
- Result
- 13/16 (81.3%) completed >= 4 WBH sessions; among 12 completers BDI-II fell 15.8 points (95% CI -22.0 to -9.70), P=0.0001; 11 no longer met MDD criteria. No serious adverse events in 79 sessions; lightheadedness (19 events in 8 participants), headache and nausea (8 events in 4 participants each) were most common, and two participants stopped sessions early for lightheadedness or jitteriness.
- Limitations
- Single arm, no control; small; 4 of 16 did not complete; CBT co-intervention makes the heat effect unattributable.
Effects of hyperthermic baths on depression, sleep and heart rate variability in patients with depressive disorder: a randomized clinical pilot trial.
Naumann J et al. BMC Complement Altern Med. 2017. PubMed 28351399 · DOI · Free full text
- Who
- medically stable outpatients with depressive disorder (ICD-10 F32/F33), HAM-D >= 18
- What
- hyperthermic baths vs sham (green light)
- Protocol
- 104 °F · mean 22.6 bath (target 30) + 33 rest min · 2/wk · 4 wk
- Measured
- HAM-D change at 2 weeks
- Result
- ITT difference 3.14 HAM-D points in favour of hyperthermic baths after 4 sessions, P=.037 by one-sided test; Cohen d 0.62 (95% CI -0.05 to 1.29), so not significant by conventional two-sided testing. Four weeks after treatment the difference was not significant (P=0.238). Adverse events (dizziness, tachycardia, tingling, heavy sweating) in 12 (86%) bath vs 9 (56%) sham participants; none serious.
- Limitations
- Pilot halted early (36 of a planned 44); one-sided testing of the primary outcome; HAM-D assessors not blinded; 6 discontinued before the 2-week assessment; retrospectively registered; hot-water immersion rather than sauna.
Effects and feasibility of hyperthermic baths in comparison to exercise as add-on treatment to usual care in depression: a randomised, controlled pilot study.
Naumann J et al. BMC Psychiatry. 2020. PubMed 33176757 · DOI · Free full text
- Who
- outpatients with moderate depression, HAM-D >= 18
- What
- hyperthermic baths vs moderate-intensity exercise program, both added to usual care
- Protocol
- 104 °F · 15-20 min · 2/wk · 8 wk
- Measured
- HAM-D change at 2 weeks
- Result
- Baseline-adjusted mean difference 4.3 HAM-D points favouring baths at 2 weeks (95% CI 2.16 to 6.42, P<0.001; ITT with last observation carried forward); per-protocol 2.7 (95% CI -0.22 to 5.69, P=0.07); at 8 weeks 2.9 (95% CI -0.40 to 6.14, P=0.084). Primary outcome missing in 5% of the bath group and 52% of the exercise group. Possibly related adverse events in 18 of 21 bath vs 7 of 11 exercise patients (dizziness, fatigue, palpitations); no serious adverse events.
- Limitations
- Open label with unblinded HAM-D assessment; 52% missing primary data in the comparator arm, imputed by carrying baseline forward, which favours baths; per-protocol and 8-week differences not significant; active comparator rather than sham; hot-water immersion rather than sauna.
Repeated thermal therapy diminishes appetite loss and subjective complaints in mildly depressed patients.
Masuda A et al. Psychosom Med. 2005. PubMed 16046381 · DOI
- Who
- mildly depressed inpatients with fatigue, appetite loss and somatic complaints
- What
- far-infrared dry sauna then 30 min blanket rest vs non-thermal therapy
- Protocol
- 140 °F · 15 (plus 30 min warm rest) min · 5/wk · 4 wk
- Measured
- somatic and mental complaints, hunger, relaxation, ghrelin
- Result
- Thermal vs non-thermal at 4 weeks: somatic complaints P<.001, hunger P<.0001, relaxation P<.0001; mental complaints P=.054; plasma ghrelin and caloric intake higher, P<.05.
- Limitations
- small; mildly depressed inpatients; no standard depression rating scale reported in abstract; unblinded
The impact of whole-body hyperthermia interventions on mood and depression - are we ready for recommendations for clinical application?
Hanusch KU et al. Int J Hyperthermia. 2019. PubMed 31159624 · DOI · Free full text
- Who
- 7 clinical studies of whole-body hyperthermia with mood or depression outcomes (mean age 46)
- What
- whole-body hyperthermia: hot baths (3 studies) or infrared heating (4 studies), single or repeated sessions over 1-6 weeks
- Protocol
- 42.55-140 (mean 66.37) min · 1-6
- Measured
- mood and depressive symptoms (pre/post effect sizes)
- Result
- 19 of 21 extracted end-points had Cohen's d of 0.8 or greater; target temperatures of 100.4-102.2 F (38-39 C) and a slower rise in core temperature were associated with larger effects. Authors concluded evidence is insufficient for general clinical recommendations.
- Limitations
- small samples; 3 of 7 studies had no control group; pre/post effect sizes inflate effects; not limited to diagnosed MDD
Association between Tub Bathing Frequency and Onset of Depression in Older Adults: A Six-Year Cohort Study from the JAGES Project
Hayasaka S et al. The Journal of the Japanese Society of Balneology, Climatology and Physical Medicine. 2024. Not in PubMed: source
- Who
- Independent older adults without depression (GDS <=4) in the Japan Gerontological Evaluation Study, surveyed 2010 and 2016 (6,452 with summer and 6,465 with winter bathing data)
- What
- Habitual home tub bathing >=7 vs 0-6 times/week (self-reported, summer and winter separately)
- Protocol
- 7+/wk
- Measured
- New-onset depression by Geriatric Depression Scale after 6 years
- Result
- OR for depression onset with >=7 vs 0-6 baths/week: summer 0.84 (95% CI 0.64-1.10); winter 0.76 (95% CI 0.59-0.98).
- Limitations
- Observational; depression defined by GDS score, not clinical diagnosis; self-reported bathing; two exposure categories only; overlaps with the JAGES sample analysed by Yagi 2019.
The Association between Tub-Bathing Frequency and the Incidence of Depressive Symptoms among Older People in Japan: JAGES Longitudinal Study
Yagi A et al. Japanese Journal of Health and Research. 2019. Not in PubMed: sourceJapanese publication; title and summary translated by SaunaLMN. Original title: 高齢者の浴槽入浴頻度と抑うつ傾向発症との関連-JAGES縦断分析
- Who
- Older adults independent in daily activities and not depressed (GDS <5) in 2010, Japan Gerontological Evaluation Study (2,159 men, 2,307 women)
- What
- Habitual home tub bathing >=7 vs 0-6 times/week in 2010 (self-reported, summer and winter separately)
- Protocol
- 7+/wk
- Measured
- Incident depressive symptoms (GDS >=5) in 2013
- Result
- Adjusted incidence rate ratio for >=7 vs 0-6 baths/week: summer 0.84 (95% CI 0.71-1.00); winter 0.77 (95% CI 0.65-0.91); adjusted for age, sex, marital status, employment, income, education and treatment for any disease.
- Limitations
- Observational; GDS-defined depressive symptoms, not clinical MDD; self-reported bathing; 3-year follow-up; overlaps with the JAGES sample analysed by Hayasaka 2024.
Protocols used in the studies
Whole-body hyperthermia trials heated participants until core temperature reached about 101.3 F (38.5 C), taking about 98-107 minutes on average, in a single session with a medical device (Janssen 2016) or in 4 sessions every other week in a far-infrared sauna dome at about 135 F (57.2 C) alongside CBT (Mason 2025). Hyperthermic-bath trials used 104 F (40 C) head-out water immersion for a mean of 20.3-22.6 minutes followed by rest, twice weekly for 4-8 weeks. The Japanese far-infrared protocol used a 140 F (60 C) sauna for 15 minutes plus 30 minutes of blanket rest, 5 days per week for 4 weeks. No trial has tested home Finnish sauna use in diagnosed depression.
What is still unknown
Optimal dose, frequency and duration; durability beyond 6-8 weeks; whether home sauna (rather than medical WBH to a core-temperature target) reproduces the effect; interaction with antidepressants; whether the IL-6 response identified in secondary analyses is a mediator; and whether benefit exceeds expectancy effects, given the 2025 null sham-controlled trial. Whether the association of habitual tub bathing with fewer new depressive symptoms in older adults reflects a heat effect or healthier, more independent bathers.
Safety
Cautions for sauna in this condition
- No serious adverse events were reported in the hyperthermia or hot-bath trials, but mild events were common: headache, lightheadedness and nausea with whole-body hyperthermia (PMID 41146956, 38743265), and dizziness, tachycardia, tingling and heavy sweating in 86% of hot-bath vs 56% of sham participants (PMID 28351399).
- Trial participants were medically screened and often medication-free; effects and safety alongside antidepressants are less studied.
- Unmedicated women with MDD had blunted skin vasodilation and delayed onset of sweating during passive heating compared with nondepressed women and SSRI-treated women (Fisher 2026, PMID 42090275), suggesting altered heat dissipation; sessions should be supervised and monitored.
- People with depression had higher rates of heat-related illness during heatwaves whether or not they took antidepressants (IRR 1.54 vs 1.64) (PMID 39648665).
- Heat therapy is an adjunct; it does not replace suicide-risk assessment or evidence-based depression treatment.
- See general-safety for cardiovascular, pregnancy, alcohol and medication contraindications.
For clinicians
Suggested rationale
In a randomized, double-blind, sham-controlled trial in adults with major depressive disorder (Janssen 2016, JAMA Psychiatry), one whole-body hyperthermia session lowered HAM-D scores by 6.5 points versus sham at 1 week and 4.3 points at 6 weeks, and an open-label trial found a 2-week benefit of hyperthermic baths over exercise (Naumann 2020); heat therapy may be considered as an adjunct to standard care, recognizing that the trials are small and short and that two sham-controlled trials (Naumann 2017; Mason 2025) did not show a conventionally significant advantage.
Suggested wording only. The treating clinician decides whether it reflects their clinical judgment for this patient.
Typical ICD-10 codes: F32.1, F32.9, F33.1. Examples only; the clinician assigns the code.
What a letter of medical necessity should containWho can write it: physicians, NPs, PAs and others