Hyperthermia, a state of elevated core body temperature, stresses the body, activating molecular mechanisms that mitigate protein damage and aggregation and promote endogenous antioxidant, repair, and degradation processes. Whole-body hyperthermia is a therapeutic strategy used to treat various medical conditions, including cancer, fibromyalgia, and others.^[1][2] Emerging evidence suggests that whole-body hyperthermia might be useful in treating depression.^[3]

While similar conceptually to recreational sauna use, whole-body hyperthermia may differ in that the nature of the duration and temperature of clinical interventions specifically targets levels of functional stress that drive key physiological responses, such as protein denaturation, alteration of cellular structures (such as the cytoskeleton and membranes), and changes in enzyme complexes needed for DNA synthesis and repair.

Learn more about sauna use in this relevant overview article.

A whole-body hyperthermia device, the Heckel HT-3000 (shown above), has been used in some clinical trials.^[3]

Whole-body hyperthermia treatment modalities

Whole-body hyperthermia is typically administered in the clinical setting using a variety of modalities. Some of these include the use of hot-water blankets, warm-water baths, heating coils, or specialized lamps that emit infrared-A radiation in a confined area or chamber. The recipient typically is exposed to the heat source until their core body temperature reaches a desired (elevated) temperature, with a maximum of approximately 42°C (107°F) for a duration of 60 minutes or longer. The recipient's body temperature, heart rate, oxygen saturation, blood pressure, cardiac function, and respiration rate are closely monitored.

Whole-body hyperthermia as an adjunct to cancer treatment

Preclinical and clinical studies have demonstrated beneficial effects of whole-body hyperthermia as an adjunct to conventional cancer therapies. A key mechanism associated with whole-body hyperthermia in cancer treatment exploits the tumor microenvironment. The blood vessels within tumors are often disorganized, resulting in areas within the tumor that are acidic or have low oxygen levels. Under these conditions, conventional radiation and chemotherapy treatments are less effective. Cancer cells are highly sensitive to heat treatment, however, and exposure to temperatures between 40°C and 44°C is cytotoxic while leaving healthy cells undamaged. Using hyperthermia in conjunction with radiation and chemotherapy has an additive effect, bolstering the effects of these therapies.

Some of the other mechanisms by which whole-body hyperthermia elicits its beneficial effects against cancer overlap those experienced during sauna use. For example, expression of heat shock proteins, which increases markedly following heat stress associated with sauna use, also increases in response to hyperthermia, especially in malignant cells, rendering them more susceptible to destruction by natural killer effector cells.^[4][5]

Fibromyalgia

Fibromyalgia is a disorder characterized by widespread musculoskeletal pain, fatigue, altered sleep, memory, and mood. An intervention study involving 67 patients with fibromyalgia who received whole-body hyperthermia treatment either once or twice a week versus standard therapy for three weeks demonstrated that one treatment per week reduced the participants' pain and improved quality of life.^[6] Similar results were observed in a larger study involving 102 patients with severe, progressive fibromyalgia.

Depression

Compelling data suggest that whole-body hyperthermia may be useful in treating depression.^[7] In particular, in a randomized, double-blind study of 30 healthy adults diagnosed with depression, participants who were exposed to a single session of whole-body hyperthermia in which core body temperature was elevated to 38.5°C (101.3°F) experienced an acute antidepressant effect that was apparent within one week of treatment and persisted for six weeks after treatment.^[3]

A 2021 study by Ashley E. Mason and colleagues tested the feasibility of using a commercially available infrared sauna to deliver whole-body hyperthermia as a potential mood-enhancing treatment.^[8] In this trial, 25 healthy adults underwent a single whole body hyperthermia session, where their core body temperature was raised to 101.3°F (38.5°C)—a level previously linked to reduced depression symptoms—over an average of 82 minutes (range 61–110 minutes), followed by a 30-minute cool-down. The study aimed to develop an accessible alternative to costly medical hyperthermia devices, which face strict FDA regulations. All participants successfully reached the target temperature without serious adverse events, proving the protocol's safety and practicality for future research or outpatient use.

Even in this non-depressed sample, the sauna session showed promising effects on mood. Participants reported significantly less negative affect immediately after whole body hyperthermia, dropping from an average score of 13.12 to 11.40 on the Positive and Negative Affect Schedule (PANAS). One week later, negative affect remained lower, and depressive symptoms, measured by the Quick Inventory of Depression Symptomatology (QIDS), showed a near-significant reduction from 4.48 to 3.48—hinting at lasting benefits. While the study didn't target individuals with Major Depressive Disorder, its findings build on prior trials showing whole body hyperthermia's antidepressant potential, suggesting that regular sauna use could offer a simple, non-pharmacologic way to boost mood. With no participants needing to stop the session and only mild discomfort reported (e.g., feeling "very hot"), this accessible sauna protocol opens the door for further exploration of whole body hyperthermia as a depression treatment.

A 2024 study also by Dr. Ashley Mason and colleagues explored the feasibility and potential benefits of combining whole-body hyperthermia via sauna with cognitive behavioral therapy (CBT) to treat major depressive disorder.^[9] In this single-arm trial, 16 adults with major depressive disorder participated in 8 weekly CBT sessions alongside either 8 weekly or 4 bi-weekly whole body hyperthermia sessions (sauna temperature of 57.2℃/135℉) using a commercial infrared sauna dome, which raised their core body temperature to 38.5°C/101.5℉. The study aimed to assess whether this integrated mind-body approach—targeting thermoregulatory processes with whole body hyperthermia and negative thinking patterns with CBT—was practical and acceptable, while also examining preliminary effects on depression symptoms. A total of 81.3% of participants completed at least 4 whole body hyperthermia sessions, though the time commitment led to some dropouts, prompting a mid-study shift to fewer sessions.

The results suggest that sauna-based whole body hyperthermia, when paired with CBT, may offer significant benefits for depression. Among the 12 participants who completed the study, 91.7% no longer met major depressive disorder criteria post-intervention, and their Beck Depression Inventory-II (BDI-II) scores dropped by an average of 15.83 points—a clinically meaningful reduction. Mood improvements were noticeable as early as after the first whole body hyperthermia session, with these gains predicting longer-term outcomes, unlike initial CBT responses. Additional benefits included reduced anxiety, better sleep, and fewer negative automatic thoughts, though cognitive flexibility improvements were not statistically significant. While the lack of a control group limits definitive efficacy claims, the study underscores sauna's potential as a feasible, non-pharmacologic addition to depression treatment, warranting further controlled research to confirm its effectiveness.

A 2024 study provided compelling evidence that whole-body hyperthermia may alleviate depression through an anti-inflammatory mechanism involving interleukin-6 (IL-6).^[10] In this 6-week, randomized, double-blind trial, 34 adults with major depressive disorder were assigned to either a single whole body hyperthermia session or a sham condition. The active whole body hyperthermia group underwent mild-intensity hyperthermia using a Heckel device, with infrared lights heating the chest and coils warming the lower extremities until their core temperature reached 38.5°C—a process taking an average of 107 minutes (range 81–140 minutes)—followed by a 60-minute cool-down phase. The study, a secondary analysis of a prior trial, screened 338 individuals, ultimately analyzing 26 participants with complete data, all free of psychotropic medications and with moderate to severe depression (baseline Hamilton Depression Rating Scale score ≥ 16).

The findings highlight sauna's potential as a depression treatment by linking whole body hyperthermia's antidepressant effects to the classical IL-6 signaling pathway. Immediately after whole body hyperthermia, the ratio of IL-6 to its soluble receptor (IL-6:sIL-6R)—a marker of anti-inflammatory activity—surged significantly compared to the sham group, but this increase was transient, not persisting at weeks 1 or 4. Crucially, higher post-whole body hyperthermia IL-6:sIL-6R ratios were strongly associated with reduced depression scores over weeks 1, 2, 4, and 6, suggesting that this acute immune response drives lasting mood improvements. Unlike chronic inflammation linked to depression, whole body hyperthermia's temporary IL-6 boost mimics beneficial effects seen in exercise, possibly triggering downstream anti-inflammatory processes. While the small sample and single-session design call for further research, this study positions whole body hyperthermia as a promising, non-pharmacologic option for depression, offering a biological basis for its mood-enhancing effects.

Learn more about these findings in this episode featuring Dr. Charles Raison

Risks and complications associated with whole-body hyperthermia

The most common side effects of whole-body hyperthermia include nausea, vomiting and diarrhea.^[11] Subcutaneous fat or muscle tissue burns can occur, as well.^[1]

Conclusion

Whole-body hyperthermia increases core body temperature for an extended duration. Scientific evidence suggests that it may be useful in treating a variety of medical conditions, including cancer, fibromyalgia, and depression. Some of the mechanisms that drive the beneficial effects of whole-body hyperthermia are similar to those elicited by regular sauna use.