Your body reacts to stress in a number of well-mapped ways. Heart rate and blood pressure speed up, muscles tense, digestion slows, and breathing becomes clipped and rapid.

All of this happens because your brain has registered the presence of some sort of threat. Whether physical or psychological, this threat triggers a trickle (or a gush) of adrenaline, noradrenaline, and other stress-related hormones. These chemical messengers shift the activity of your nervous and immune systems in ways that are meant to help you either flee from danger or weather some kind of ordeal or confrontation.

None of this tends to be a problem if it happens in moderation. Your body is designed to experience plenty of stress-related activation, and there’s some evidence that short bouts of stress may helpfully sharpen your focus, strengthen your memory, and provide other temporary benefits without doing any lasting damage. (If the stress response were wholly bad, your body wouldn’t engage it so readily.)

But if stress is too severe or too persistent, much can go wrong.

Chronic stress promotes low-grade, systemic inflammation, and it’s associated with an increased risk for pretty much all the major disorders of the mind and body — from anxiety and depression to heart disease. Pick a medical condition, any medical condition, and research has probably shown that chronic stress contributes to its development or makes it worse.

As researchers have studied the many overlapping risks associated with chronic stress, they’ve also identified helpful methods of stress relief or mitigation. That work has repeatedly found that Eastern wellness or contemplative practices, such as meditation, yoga, and tai chi — as well as stripped-down, Westernized versions of these activities, such as mindfulness and progressive muscle relaxation — produce potent anti-stress benefits.

While each of these practices is unique, a single unifying feature ties them all together: the breath.

Calm and controlled breathing quickly and dramatically snuffs out stress by stimulating the vagus nerve

For a 2018 paper in Frontiers in Human Neuroscience, researchers from Germany and the Netherlands explored the role of “respiratory discipline” — basically, slow and measured breathing — in the management of stress.

In that paper, they make a compelling case that calm and controlled breathing quickly and dramatically snuffs out stress by stimulating the vagus nerve.

The vagus nerve, which experts have nicknamed the body’s “great wandering protector,” is actually a lengthy, branching network of nerves that extends from your brain down into your body, where it communicates with many of your organs and systems.

Much about the vagus nerve remains a mystery, but its activity is closely linked to states of rest and relaxation.

While stress and its attendant fight-or-flight response switches on your autonomic nervous system, the vagus nerve activates the parasympathetic nervous system, which dampens autonomic activity and all its problematic effects — including inflammation.

“The vagal nerve, as a proponent of the parasympathetic nervous system (PNS), is the prime candidate in explaining the effects of contemplative practices on health, mental health and cognition,” the Frontiers study team wrote.

Vagus nerve stimulation is currently used to treat a range of conditions. According to a 2018 review in the Journal of Inflammatory Research, this treatment is FDA approved for epilepsy and depression, and it’s increasingly employed as a therapy for inflammation-linked disorders of the brain and body, everything from lung disease and rheumatoid arthritis to Alzheimer’s and diabetes.

It may seem farfetched that something as simple (and cost-free) as measured breathing could likewise stimulate the vagus nerve and produce similar medical benefits. But more and more, evidence supports this theory.

In their Frontiers paper, the European researchers explain that many different breathing exercises seem to be beneficial. Diaphragmatic (or “belly”) breathing, box breathing, and other techniques all switch on the vagus nerve and reduce stress. But summing up the research to date, they say that slow, calm breathing — something on the order of six complete breaths per minute, with an emphasis on long and full exhalations — seems to be most effective.

The ability of the breath to make us better is “such an unremarkable fact, so plainly observable” that we all tend to ignore it, they write. But the more we learn about the breath and its association with the vagus nerve, the more it seems like an antidote to many of our most pressing health problems.