Whole-Body Hyperthermia and Far Infrared in Major Depressive Disorder
A Clinical Review of the Sham-Controlled Evidence, the Sham Problem, and the Dose Gap
Overview
Major depressive disorder (MDD) has a small but genuine body of sham-controlled whole-body hyperthermia (WBH) research, which distinguishes it from most conditions in this series. It also carries three structural limits that prevent translation to routine far infrared (FIR) sauna use: a dose gap (trial protocols raised core temperature to 38.5°C, not the modest rise of a conventional session), a sham problem (the most recent randomized pilot could not separate heat from other effects), and an absence of modality-specific evidence (no trial isolates FIR from other heating methods). This review states each plainly. FIR or WBH should not be represented as an established treatment for depression.
Direct Human Evidence: Randomized Sham-Controlled Trial
Single small randomized trialJanssen et al. ( JAMA Psychiatry 2016;73(8):789–795; NCT01625546 ) randomized adults with MDD (medically healthy, aged 18–65, free of psychotropic medication, baseline 17-item Hamilton Depression Rating Scale [HDRS] score of 16 or greater; registry criteria specify MDD without psychotic features) to a single session of WBH or a sham session in a double-blind design.
Active WBH produced significantly lower HDRS scores than sham across the 6-week post-intervention period (between-group difference at week 1: −6.53, 95% CI −9.90 to −3.16, P<.001; week 2: −6.35, 95% CI −9.95 to −2.74, P=.001; week 4: −4.50, 95% CI −8.17 to −0.84, P=.02; week 6: −4.27). Adverse events were generally mild. The authors concluded WBH “holds promise as a safe, rapid-acting, antidepressant modality with a prolonged therapeutic benefit.”
Blinding and Trial Limits
Blinding was imperfect: immediately after the intervention, 15 participants (93.8%) randomized to WBH and 10 (71.4%) randomized to sham believed they had received WBH. Heating in this line of work targeted a core body temperature of 38.5°C using an infrared heating device (the Heckel HT3000 in the group's earlier studies). It is a single small trial, and expectancy effects cannot be excluded.
An earlier open-label study in 16 adults with MDD ( Hanusch et al. 2013, Am J Psychiatry 170(7):802–804 ) preceded it and lacked a placebo control, which motivated the sham-controlled design.
Combined WBH + CBT: What the Pilot Trials Can and Cannot Show
The Uncontrolled Feasibility Study
A single-arm feasibility study of WBH plus cognitive behavioral therapy (CBT) found that among participants who completed treatment, 91.7% no longer met criteria for MDD and the mean BDI-II reduction was 15.8 points ( Mason et al. 2024, Int J Hyperthermia 41(1):2351459 ). This is the source of the widely circulated “~90% no longer depressed after infrared sauna” figure. It is an uncontrolled result.
The Randomized Pilot
The subsequent randomized single-blind pilot ( Mason et al. 2025, Glob Adv Integr Med Health 14:27536130251387714; PMID 41146956; NCT05708976 ) enrolled 30 adults with MDD (not using antidepressants or thermoregulation-altering medications; pregnancy excluded).
All received eight weekly CBT sessions and were randomized to four biweekly sessions of WBH (Clearlight Curve Sauna Dome, far-infrared elements of carbon fiber and ceramic; ambient approximately 57.2°C; heated until rectal core temperature reached 38.5°C or 140 minutes elapsed) or sham WBH (ambient approximately 46.0°C; heated only until core temperature rose 0.1°C).
Staff remained present, applied cool cloths to the head and neck, and monitored core temperature by rectal probe. Mean WBH session length was 98.5 minutes; 38 of 53 WBH sessions reached the 38.5°C target.
Both Groups Improved
Both arms improved substantially: mean BDI-II change −19.07 (SE 2.69) with WBH and −21.10 (SE 2.41) with sham; the proportion no longer meeting DSM-5 MDD criteria was 80.0% (12/15) with WBH and 92.9% (13/14) with sham (86.2%, 25 of 29, combined).
The primary outcome was acceptability, and the authors state the pilot was not powered or designed for between-arm comparison. Sham credibility was poor: all WBH participants correctly believed they were in the active arm, while only 42.9% (6/14) of sham participants correctly believed they received sham.
Thermal overshoot (a fall of ≥0.1°C below baseline core temperature after heating began) occurred in 94.7% of sham and 98.1% of WBH sessions. The authors conclude that the sham arm “was not fully credible and may have exerted antidepressant effects,” that no CBT-alone arm was included, and that a heat-free credible comparator and a 2×2 factorial design are needed.
Adverse Events
Adverse events in the WBH arm were mild and expected: headache (28 events in 13 of 15 participants; 89.3% resolved by end of the session day), lightheadedness (15 events, 7 participants), and nausea (8 events, 5 participants). No serious adverse events occurred in the trial.
Interpretation
What the Evidence Does and Does Not Support
- Supported: a small sham-controlled RCT (Janssen 2016) showing lower HDRS scores after a single supervised WBH session in unmedicated adults with MDD, consistent with a thermoregulatory hypothesis in which strong heating engages cooling responses relevant to mood.
- Not separable: in the 2025 pilot, the heat-based sham arm improved as much as or more than the active arm, so the effect of heat cannot be distinguished from CBT, expectancy, or an active sham. The authors themselves flag this.
- Dose gap: protocols targeted a core temperature of 38.5°C, averaging roughly 100 minutes of supervised heating with core-temperature monitoring. Core temperature was not the target of, or measured in, conventional FIR sauna protocols. No trial has tested a standard session for depression, and no trial has used a Relax Saunas device.
- No modality specificity: no trial compares FIR against other heating modalities for mood, and the heat-independent NRF2 findings in the vascular literature (Bagabir 2025) should not be transferred to depression outcomes.
- Population limits: participants were unmedicated (recent antidepressant use excluded because of effects on thermoregulation and reported limited WBH benefit in medicated patients), medically healthy, and had MDD without psychotic features. Bipolar depression, psychosis, pregnancy, and medicated populations are not covered.
Correcting Circulating Claims
Practitioner Advisory: Claims Patients May Bring
- “About 90% of people in a UCSF infrared sauna program no longer met criteria for depression.” The figure derives from an uncontrolled feasibility study (Mason 2024) of combined WBH and CBT. The later randomized pilot found comparable or greater improvement in the sham-heat arm.
- Vendor content presenting the UCSF work as proof that infrared sauna treats depression overstates it: the trials tested supervised hyperthermia to a core-temperature target, alone or alongside CBT, and the most recent trial was a feasibility pilot not powered for efficacy.
Safety and Patient Selection
Clinical Cautions
- Depression care should not be displaced: first-line psychotherapy and pharmacotherapy remain the standard. Patients should not reduce or discontinue prescribed treatment because of sauna use, and suicidality warrants standard clinical assessment and crisis resources (in the US, call or text 988) before any adjunct discussion.
- Medications affecting thermoregulation, sweating, or fluid balance (for example lithium, anticholinergic agents, some antipsychotics, and some antidepressants; hyperhidrosis with second-generation antidepressants is documented) warrant prescriber review before heat exposure. This is a general pharmacologic caution, not a finding of the trials above.
- Trial safeguards (rectal core-temperature monitoring, staff present, head cooling, hydration) are not replicable in a home setting; trial-level heat exposure produced common but mild headache, lightheadedness, and nausea.
- Pregnancy was an exclusion criterion. No evidence exists in bipolar disorder, psychotic depression, or cardiovascular disease populations; see this series' companion cardiovascular and conduction-disease reviews.
Evidence Grading Summary
| Domain | Mechanism | Human Evidence | Tier |
|---|---|---|---|
| Single-session WBH vs sham (unmedicated MDD) | Thermoregulatory hypothesis | Janssen 2016: lower HDRS across 6 weeks; imperfect blinding | Direct, Single Small RCT |
| WBH + CBT vs sham heat + CBT | Same hypothesis | Mason 2025: both arms improved; not powered; sham possibly active | Preliminary, Not Interpretable for Efficacy |
| WBH + CBT, uncontrolled | Same hypothesis | Mason 2024: 91.7% of completers no longer met MDD; no control | Preliminary |
| Standard-dose FIR sauna session | None specific | No trial identified | Absent |
| FIR-specific vs other heat on mood | None specific | No trial identified | Absent |
| Medicated, bipolar, psychotic, or pregnant patients | N/A | Excluded or not studied | Absent |
On smaller screens, swipe horizontally to view the full table.
Clinical Positioning
Whole-body hyperthermia has a real but early antidepressant signal, supported by one small sham-controlled RCT and complicated by a follow-up pilot in which the heat-based sham improved as much as the active arm.
Far infrared sauna, at conventional doses and without core-temperature targets, has not been tested for depression. It may be discussed with patients as a relaxation and sleep-supportive practice within their existing care, never as a depression treatment, and practitioners should be prepared to correct the “90% no longer depressed” figure if a patient raises it.
References
Janssen, C.W., Lowry, C.A., Mehl, M.R., et al. (2016). Whole-Body Hyperthermia for the Treatment of Major Depressive Disorder: A Randomized Clinical Trial. JAMA Psychiatry, 73(8), 789–795. doi:10.1001/jamapsychiatry.2016.1031. PMID 27172277. ClinicalTrials.gov NCT01625546.
Hanusch, K.U., Janssen, C.H., Billheimer, D., et al. (2013). Whole-body hyperthermia for the treatment of major depression: associations with thermoregulatory cooling. Am J Psychiatry, 170(7), 802–804. doi:10.1176/appi.ajp.2013.12111395.
Mason, A.E., Chowdhary, A., Hartogensis, W., et al. (2024). Feasibility and acceptability of an integrated mind-body intervention for depression: whole-body hyperthermia (WBH) and cognitive behavioral therapy (CBT). Int J Hyperthermia, 41(1), 2351459. doi:10.1080/02656736.2024.2351459.
Mason, A.E., Hartogensis, W., Chowdhary, A., et al. (2025). A Randomized Trial Testing a Novel Mind and Body Intervention for Depression: Cognitive Behavioral Therapy (CBT) and Whole-Body Hyperthermia (WBH). Glob Adv Integr Med Health, 14, 27536130251387714. doi:10.1177/27536130251387714. PMID 41146956. ClinicalTrials.gov NCT05708976.
Hanusch, K.U. & Janssen, C.W. (2019). The impact of whole-body hyperthermia interventions on mood and depression — are we ready for recommendations for clinical application? Int J Hyperthermia, 36, 573–581. doi:10.1080/02656736.2019.1612103.