Could Saunas Cure Depression? Investigating a Hot New Theory.

8 min read

I’m lying on a hospital bed, drenched in sweat. My body feels like it is burning up from the inside. I want that to stop.

Outside, it is a lovely summer day in the resort town of Vail, Colorado, with tourists whizzing around on e-bikes or heading off on relaxing mountain hikes. In this sterile, fluorescent-lit room, machines beep and staffers hover anxiously about, watching me suffer. A kind woman named Ashley Mason presses chilled cloths and ice cubes to my forehead and temples, trying to keep me cool. You’re doing great, she murmurs.

There is no hope of escape, because I am encased in a green metal cylinder that looks like part of a rocket fuselage but is in fact a personal-sized infrared sauna. My head is exposed, but the rest of me is tucked inside this tube, which is lined with heating elements that are slow roasting me with 1,000 watts of power.

This is by far the least fun “sauna” that I have ever experienced.

But it’s not really meant to be fun. This is research, which means that I have agreed to stick a temperature probe where probes are stuck. The upside is that I am unlikely to die, because my core temperature is being carefully monitored by said probe.

I volunteered to be a test subject for a novel clinical trial co-designed by Mason, the kind woman with the ice cubes, who is a professor of psychology at the University of California at San Francisco. Her idea is to test the effects of “whole-body hyperthermia”—basically, getting people really hot—on symptoms of severe depression. It’s an idea that occupies the cutting edge of psychological research, albeit with less hype than studies of psychedelic drugs. Mason and her colleagues hope that this study might ultimately help validate heat treatment as a legitimate mental-health protocol that could give hope to millions of suffering people.

Lying in the tube, I have doubts. Data and common sense tell us that heatwaves are miserable; how could getting hot help people feel less depressed?

Yet this crazy-sounding idea is supported by some compelling evidence. For some unknown reason, depressed people seem to struggle in the heat even more than the rest of us. Physicians and researchers have long observed that patients with major depression don’t sweat very much; sometimes not at all. At the same time, these folks also seem to maintain a higher-than-normal resting body temperature, most of the time.

This curious symptom had been widely noted in passing, mostly in smaller studies, but Mason had helped to confirm it in a huge, 20,000-subject dataset of healthcare workers compiled during Covid. Even more intriguing, when very depressed people received treatment, in the form of drugs or electroshock therapy, their body temperature would revert to normal, some studies found. “Our hypothesis is that people with depression have a harder time thermoregulating,” Mason told me. “The treatment gives it a workout.”

Does it ever.

I am only the second person to try out this grueling hot-tube protocol; when I visited in June 2024, the study was just getting started. The first test patient was Vail Behavioral Health executive director Chris Lindley, who told me that it was “one of the hardest things I’ve ever done.”

I later learned that Lindley wakes up every morning at 5 a.m. to do high-intensity interval workouts, followed by a plunge into ice-cold water. Oh, and while serving with a medical detachment in Iraq, his unit survived a suicide bombing. Yet this was the hardest thing he’s ever done. On the other hand, Lindley noted, he did feel better after the treatment. “I’m a happy, optimistic person, and even I noticed an effect,” he said.

This study is called “CHILL’D” (for “Cold and Heat to Investigate Lowered Levels of Depression”), because at some point, I’ll be required to submerge myself in a tub of 49-degree-F water that is sitting just a few tantalizing feet away. As far as anyone knows, this is the first-ever trial combining heat treatment and a cold plunge for depression. It grows out of decades of tantalizing data, from sauna studies and small random experiments, suggesting that targeted heat exposure—and cold—may have some significant mental-health benefits.

This is not a new idea. The Finns and Russians and Ukrainians, among others, have combined hot sauna and cold plunging for centuries. One of the most curious but unexplained findings of long-term Finnish sauna studies was that frequent sauna users—many of whom presumably cold-dipped in between sauna rounds—experienced fewer psychotic episodes over their lifetimes.

It requires all my sisu, my sauna grit, not to simply quit.

There is at least some suggestion that cold plunging itself could have a beneficial effect on symptoms of depression. Dunking ourselves in cold water substantially boosts blood levels of both dopamine and noradrenaline, a neurotransmitter that increases alertness, cognitive function, and blood pressure—yet that does not mean they are also elevated in the brain. Even so, cold-water immersion does lower inflammation, boosts serotonin and beta-endorphins, and stimulates the vagus nerve.

But nobody had really dug in to figure out if heat plus cold could be turned into a legitimate mental-health treatment, as opposed to an Instagram biohack.

Now it is being put to the test, across the street from some of the most expensive ski lifts in the world. Depression is their primary target, because it is one of the most prevalent medical conditions. It’s already widely treated, but the standard medications for depression have been falling short. In the US, one in nine adults took some form of antidepressant in 2023, according to the CDC. They may be effective for some, but have not proved to be the “cure” for depression that many hoped they would be. Data shows that for every five people who receive an antidepressant, one is helped.

This research raised the question: What if, instead of antidepressant drugs, they simply gave depressed patients a fever?

Which is why I’m lying in the Hot Tube: They’re trying to give me a fever.

Or at least mimic one, by heating my core temperature above 101.3 degrees F—the level at which physiological changes linked to heat adaptation begin to occur. A handful of smaller studies have found that heating severely depressed patients up to this level has radically relieved their symptoms—and that the effect can last up to six weeks. Unfortunately, it’s taking a while. It requires all my sisu, my sauna grit, not to simply quit. If Mason stops with the cold compresses, if she pauses even for half a minute, I’ve decided, I’m out.

As I stare up at the hospital’s dropped ceiling and fluorescent lights, trying not to think about my mounting discomfort, I start to wonder, how depressed do you have to be to make this seem appealing?

Pretty depressed. This study is only open to patients who qualify as “severely depressed,” according to a widely used clinical depression “instrument”; a quiz known as Beck’s depression inventory.

Officially, I am here in Colorado as an observer, but my interest in this question is more than strictly professional. I’m not severely, permanently depressed, I don’t think, but I might have come close to that, a time or two in my life. Lately, I had been feeling a little bit down for various reasons. A couple of weeks before driving to Vail, I had taken the Beck’s inventory. The results confirmed what I already knew, which was that I had a solid case of moderate depression. And I had done nothing about it.

Which is the real reason why I had volunteered to undergo the treatment. But I am beginning to doubt that marinating in my own sweat for an hour and a half will make me any less mopey.

I’m done, I think, just as Chloe announces, “You’re done!”

The meat thermometer lodged in my rear has reached the magical temperature of 101.3. She switches off the sauna, and I “rest” for another two minutes, like a tenderloin roast, before she slides open the tube, exposing my sweaty torso to the magically cool air. It’s a huge, indescribable relief. But when I try to sit up too quickly, my head swims.

Guided by unseen hands, I shuffle over to a white porcelain tub that looks like it belongs in a luxury hotel bathroom. I haven’t looked forward to a cold plunge this much in forever. I step in carefully, one foot and then the other, and then drop my butt right down into the water.

This is what I’ve been dreaming of, for at least the last hour. Nice and cold, as advertised. But it’s actually too cold; my skin is burning. Chloe is there with the stopwatch, and it takes so long for her to say, “You’ve been in a minute and a half.”

I take deep breaths, and clasp my palms together, Namaste-style, until she calls time.

Still groggy, I shuffle across the hall to shower and get dressed. I am too sauna-drunk to drive, so I ride back with the researchers, who pepper me with questions. What was it like? How do I feel?

I don’t know. I do not feel notably less depressed. I do feel physically wrecked. I need food—large amounts of really unhealthy, salty foods. We stop at the first restaurant we see, where I inhale a burger with sweet potato fries and a beer. I go to bed early, only to lie awake with a crushing migraine. After a warm midnight shower, some salty snacks, and three ibuprofen washed down with Gatorade—I finally fall asleep, feeling skeptical about the whole thing.

My home in Salt Lake City is about seven hours by car from Vail. To break up the trip, I stop at Glenwood Springs, Colorado, a classic old pool and hot springs complex dating to the late nineteenth century. As I float, I ruminate on the Treatment. I don’t see how it’s going to help anyone; I’m mostly glad that it’s over. Do I even like heat anymore? The Glenwood pools feel more like my speed—and in fact some studies have suggested that plain old hot-water bathing, like in a bathtub, can have its own antidepressant effects.

Back on the road, something strange happens. Driving is one of my least favorite activities, because it is so deadly boring, yet deadly dangerous. I’m always on edge.

But this time is different. Past Grand Junction, dark clouds begin massing to the south—this is a pretty big storm. The wind picks up, whipping tumbleweeds across the roadway and pushing my car toward the shoulder. Rain bands drum on the windshield. Trucks are swerving.

Normally, I would be freaking out in a situation like this. But I am focused, floating on a feeling of pure liquid calm. I set the cruise control to 85 miles per hour, and let the highway draw me home.

I feel zero anxiety whatsoever. I turn the radio on and remember that tonight is the first Presidential debate of the 2024 election. I listen to two minutes of grumpy old men arguing about golf, then switch it off to ride home in untroubled silence.