Illustration: Kieran Blakey

The Nuance

‘Biofeedback’ Could Ease Headaches, Anxiety — and Maybe a Lot Else

By providing a window onto the body’s inner workings, biofeedback could help people control what was once thought to be ungovernable

The man’s boasts were outlandish. Wim Hof, a 51-year-old Dutch endurance athlete, claimed that he could voluntarily control his own immune system — ramping its activity up or down at will. Moreover, he said that he could teach this skill to others.

Hof’s assertions might never have been put to the test but for the fact that he held several remarkable world records — including one for the longest time spent submerged neck-deep in an ice bath, and another for the fastest half marathon run barefoot on snow. His accomplishments earned him the nickname “the Iceman” and generated enough public interest — at least in the Netherlands — that scientists decided to investigate his claims.

For a 2012 study that appeared in the journal Psychosomatic Medicine, a team of Dutch researchers injected Hof with a toxin from E. coli bacteria. In past experiments, the toxin had reliably caused nausea and other symptoms and had also produced steep elevations in blood biomarkers of inflammation. After receiving the injection, Hof reported almost no symptoms, and his blood samples revealed “a remarkably mild inflammatory response,” the study authors reported.

In 2014, a follow-up study repeated the experiment using a group of 12 people who had trained using Hof’s methods. Blood samples indicated that, like Hof, they were able to exert some control over their body’s inflammatory response, which is a component of the immune system usually thought to be wholly involuntary and that, when overactive, can cause or contribute to a wide range of health problems.

“Hof had effectively found the off-switch for his immune system,” says Scott Carney, an investigative journalist who details his own experience with Hof’s techniques in the 2017 bestseller What Doesn’t Kill Us. “The [Hof] studies showed that something that should be impossible to do was possible.”

What does Hof’s method entail? Carney says it combines meditation and breathing exercises with cold exposures, such as a frigid shower. During these cold-exposure intervals, which Carney duly undertook, he would concentrate on speeding up his own metabolism in order to generate body heat and stop himself from shaking or shivering. Through this and related exercises, “you start to sort of gain control of internal bodily processes that we don’t generally try to access,” he says. “I’ve seen people use this for remission of Crohn’s, arthritis — just crazy things.”

It’s possible that biofeedback, by giving people a real-time look at the internal workings of their nervous system, can facilitate these self-calming practices.

While all of this may sound wild and far-fetched, some of Hof’s practices dovetail with a long-studied form of therapy known as biofeedback. “As the word suggests, biofeedback involves feeding back to the patient their own bio-signals, such as blood pressure or heart rate variability or muscle tension — anything that the body is displaying as a result of activity of the autonomic nervous system,” says Stefan Hofmann, PhD, a professor of psychology at Boston University. (Hofmann is not related to Hof.)

The autonomic nervous system (ANS) is so named because its processes are largely automatic — meaning involuntary and unconscious. The ANS plays a role in breathing, heart rate, digestion, thermoregulation, and a lot else. While Hof’s unconventional methods use the body’s response to cold as its source of biofeedback, this therapy has traditionally used specialized sensors to produce real-time measures of a person’s heart rate variability or other ANS-generated internal signals.

“By feeding these signals back to people, they can, to some extent, gain control over them,” Hofmann explains.

The research on biofeedback

Researchers have been exploring biofeedback since the 1960s. Some of the strongest work in support of its therapeutic power has examined its effect among people with headaches.

A 2019 review from the U.S. Department of Veterans Affairs found “high-confidence evidence that biofeedback is effective for reducing the frequency, duration, and intensity of migraine and tension-type headaches.”

While biofeedback techniques vary, many headache studies have involved hooking people up to electromyogram (EMG) sensors that measure electrical activity in the skin and muscles, which ebbs and flows in response to headache pain. This EMG data is “fed back” to a person as sounds, images, or both. For example, as a person’s headache worsens, a computer connected to the EMG may display a colored circle that contracts or grows red. “You might focus on widening the circle or changing its color,” Hofmann says. By doing this, people often find that they’re able to turn down their headache’s intensity.

Apart from its role in headache management, EMG biofeedback has helped people recover muscle function and mobility following a stroke. The technique can also treat incontinence, blood flow problems, and — as the Hof research suggests — maybe even inflammation and symptoms of some autoimmune disorders. A 2019 study from researchers at UCLA found that virtual reality–based biofeedback — using VR headsets to show people visual representations of their own breathing patterns — helped to reduce pain among people with rheumatoid arthritis and lupus. Researchers have also found that biofeedback, perhaps by increasing activity in the vagus nerve, may have some anti-inflammatory effects.

More recently, scientists have started looking at biofeedback as a treatment for anxiety disorders. A 2018 study in the journal Stress found that biofeedback lowered symptoms of burnout and improved math performance among a group of college students. Boston University’s Hofmann co-authored a 2017 research review that found biofeedback based on heart rate variability — a measure of the time between heart beats — could produce a large drop in self-reported stress and anxiety.

“There has been a long-standing view among behavioral scientists that if you can feel and perceive something, then you may be able to control it.”

How does biofeedback do all this? “That’s still a bit of a mystery,” Hofmann says. But there are theories. He explains that with some concentration and practice, people have the ability to regulate their own breathing or muscle tension, which can have a calming effect on heart rate, blood pressure, and other elements of the autonomic nervous system that are associated with unhealthy states of arousal. It’s possible that biofeedback, by giving people a real-time look at the internal workings of their nervous system, can facilitate these self-calming practices.

“There has been a long-standing view among behavioral scientists that if you can feel and perceive something, then you may be able to control it,” adds Hugo Critchley, MD, PhD, chair of psychiatry at the University of Sussex in the U.K.

One of Critchley’s primary areas of research concerns the ways in which the mind, brain, and body interact during states of arousal. He points out that, somewhat surprisingly, research on experienced Buddhist meditators has found that they are no better than non-meditators when it comes to detecting their own heartbeat.

By giving people a sharper view of their heartbeat and other internal states, biofeedback may help people take the wheel of processes or functions that were long presumed to be ungovernable, Critchley says.

Bringing biofeedback out of the lab

In the past, technologies capable of providing people with accurate, real-time biofeedback tended to be expensive and cumbersome. But that’s changing. “There’s a revolution going on with high-tech companies measuring bio-signals, and biofeedback will have a role in that,” Hofmann says.

Some companies are planning to roll out VR headset programs that work with the Apple Watch and other wearable heart rate monitors to provide helpful biofeedback measures. And already there are a number of commercial wearables that are capable of measuring heart rate variability. (This is different from a simple heart rate monitor, which Hofmann says is not a helpful biofeedback output.)

A lot more research is needed to clarify biofeedback’s therapeutic uses and mechanisms of action. It could turn out that coupling biofeedback with meditation or muscle-relaxation techniques could enhance these practices’ well-studied health benefits. It’s also possible — though far from certain — that biofeedback could help people turn down harmful inflammation or other arousal-linked internal states.

“If you’re able to be more aware of what’s going on in your body, that can give you better control of arousal,” Critchley says. “And a lot of arousal is inappropriate.”

I write about health and science. I live in Detroit with my wife and kids. I’m trying to learn German, but my progress so far is nicht gut.

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