Beyond Relaxation: Saunas as a Potential Treatment for Depression 

Exploring heat therapy’s surprising role in alleviating depression symptoms.

By Gillian Feinglass

Picture this: after a long, hard day, you step into a sauna, take a deep breath, and for a moment, it almost feels as though the heat is melting your worries away. Saunas have long been associated with self-care, leaving people feeling rejuvenated and refreshed. But what if saunas offer more than just sweat and relaxation? What if these heated sanctuaries hold the key to treating one of society’s most prevalent mental health disorders – depression? Promising new research shows that exposing depressed people to heat therapy may help treat depression through a nonpharmacological approach. This heat therapy is not delivered by your typical gym sauna but has somewhat similar heating effects. Instead, this intervention utilizes a medical-grade infrared whole-body heating device that has been used to treat cancer and fibromyalgia. 

How might this work? Inflammation is an essential element of the body’s immune response that protects against a wide range of threats to health and well-being. It’s well documented that major depressive disorder (MDD) is associated with chronic inflammation, in which the body’s inflammatory response becomes dysregulated and continues to function despite no infection or injury. When the body undergoes extreme heat, the immune system is activated and produces cytokines, specifically Interleukin-6 (IL-6), which are small signaling proteins that regulate the body’s immune response. While IL-6 is classified as a pro-inflammatory cytokine, temporary rises in IL-6 stimulated by infection, exercise, or heat are considered to be good for the body. Brief increases in IL-6 indicate that the body is responding appropriately to potential threats and, in turn, decreases inflammation. As a result, there has been great interest in investigating the effectiveness of anti-inflammatory interventions, such as heat therapy, to reduce depressive symptoms in individuals with chronic inflammation. 

Linking heat and immune response to depression

A small study published in April 2023 in the journal Translational Psychiatry by a group of researchers around the United States explored the possibility of us heat as a potential therapeutic intervention for people with MDD. Researchers measured cytokine levels in patients with MDD to evaluate the therapeutic effects of mild-intensity whole-body hyperthermia on inflammation. They measured cytokine levels before and after the treatment. The researchers’ goal was to determine if the therapy’s positive impact on depression was associated with changes in inflammation. 

The study hypothesized that whole-body hyperthermia would briefly elevate patients’ IL-6 production, thereby reducing inflammation and, in turn, alleviating depressive symptoms. They were correct. Results revealed that whole-body hyperthermia caused both an acute and sustained reduction in depressive symptoms. However, researchers found that their intervention did not have a long-lasting effect on immune biomarkers, measurable indicators that can tell us information about the state of the health of our bodies, that they anticipated. While whole-body hyperthermia markedly improved depressive symptoms, it did not significantly reduce the immune system’s key biomarkers, particularly pro-inflammatory cytokines. Instead, the treatment led to an unexpectedly sharp increase in the proinflammatory cytokine IL-6. Such an increase is traditionally associated with inflammation, depressive symptoms, and health problems.

However, there was a beneficial relationship between the increase in IL-6 and improved depression symptoms. The unforeseen association reveals the complex relationship between hyperthermia, immune responses, and depression that requires more investigation.  

“This study was a landmark study,” says neuroscientist and clinical psychologist Michael Flux, the lead statistical designer and analyst on the study. However, “it’s not like taking a pill and making it all better.” Flux advocates for promoting wellness rather than just treating dysfunction. Instead of viewing whole-body hyperthermia as a quick fix for depression, he emphasizes that the intervention should be viewed as a helpful mechanism for maintaining wellness. 

Mimicking the feeling of heat

The double-blind, randomized trial included 30 males and females aged 18 to 65 who met the Diagnostic and Statistical Manual of Mental Disorders criteria for MDD. The study included two randomized groups: a group that received the treatment and a placebo group that encountered a sham treatment designed to mimic the actual treatment but had no therapeutic effect. To prevent bias, neither the participants nor the researchers knew what treatment the participants were undergoing. One group was given the true treatment; they were exposed to infrared lights in a chamber until their core body temperature reached 101.3 Fahrenheit, which often took 60 minutes or longer. Charles Raison, psychiatrist and professor at the University of Wisconsin-Madison School of Medicine and Public Health, who served as the study’s principal investigator, said that he underwent the heating treatment himself and had never felt so hot in his life. 

The placebo group received orange-color non-heating lights and mild heat to increase believability. This was successful as 71% of the sham-treated patients reported that they thought they had received the true whole-body hyperthermia treatment. After one treatment, there was a significant reduction in depression symptoms. These effects were sustained throughout the following six weeks that the participants were monitored when compared to the sham group. Following the treatment, researchers utilized the Hamilton Depression Rating Scale multiple times in the six weeks after the treatment. 

“The data consistently suggests that a single treatment has an antidepressant effect that is clinically meaningful for many people with depression,” says Raison (who is also a visiting professor in the Center for the Study of Human Health at Emory University School). “But we don’t know how to optimize the treatment yet.” He emphasized that more research must be done on a grander scale to substantiate the study’s findings and determine optimal treatment protocols. 

Designing the next steps in research

Joshua Berman, a psychiatrist and assistant professor at Columbia University Irving Medical Center, who is unconnected to this study, focuses on cutting-edge treatments for mood disorders. He echoed the importance of further research, stating, “There needs to be more data. The next step is looking at different populations and types of depression.” He added that “the advantage of something like raising core body temperature, which is a rather unusual mechanism, is that it will likely be used for people for whom other things either aren’t tolerated or don’t work.”

The potential of this treatment inspires hope for people living with MDD, especially those who are treatment-resistant.  Raison suggests that there is no downside to trying this intervention for those living with depression, although more research must be done to show its benefits on a larger scale and for doctors to recommend it with certainty. Many do not have access to an infrared machine that can deliver heat at this level. However, Raison suggests spending around 40 minutes in a sauna and monitoring body temperature with a rectal thermometer (ensuring it never exceeds 101.3 degrees Fahrenheit). Depression can be a debilitating disorder, and many have found that they are resistant to common treatments. So next time you’re passing by the sauna at the gym, “if you’re depressed, it’s worth a try,” says Raison.