Someone points us to the above-titled news article from 2017 which reported:

Scientists at Stanford University may have uncovered for the first time why taking deep breaths can be so calming. The research, on a tiny group of neurons deep within the brains of mice, also underscores just how intricate and pervasive the links are within our body between breathing, thinking, behaving and feeling. . . .

Hhow the mind and body regulate breathing and vice versa at the cellular level has remained largely mysterious. More than 25 years ago, researchers at the University of California at Los Angeles first discovered a small bundle of about 3,000 interlinked neurons inside the brainstems of animals, including people, that seem to control most aspects of breathing. They dubbed these neurons the breathing pacemaker. . . .

Recently, a group of scientists at Stanford and other universities, including some of the U.C.L.A. researchers, began using sophisticated new genetics techniques to study individual neurons in the pacemaker. . . .

The scientists confirmed that idea in a remarkable study published last year in Nature, in which they bred mice with a single type of pacemaker cell that could be disabled. When they injected the animals with a virus that killed only those cells, the mice stopped sighing . . . Without instructions from these cells, the sighing stopped. . . .

So for the newest study, which was published recently in Science, the researchers carefully disabled yet another type of breathing-related neuron in mice. Afterward, the animals at first seemed unchanged. They sighed, yawned and otherwise breathed just as before.

But when the mice were placed in unfamiliar cages, which normally would incite jittery exploring and lots of nervous sniffing — a form of rapid breathing — the animals instead sat serenely grooming themselves.

“They were, for mice, remarkably chill,” says Dr. Mark Krasnow, a professor of biochemistry at Stanford who oversaw the research.

To better understand why, the researchers next looked at brain tissue from the mice to determine whether and how the disabled neurons might connect to other parts of the brain.

It turned out that the particular neurons in question showed direct biological links to a portion of the brain that is known to be involved in arousal. This area sends signals to multiple other parts of the brain that, together, direct us to wake up, be alert and, sometimes, become anxious or frantic.

In the mellow mice, this area of the brain remained quiet.

“What we think was going on” was that the disabled neurons normally would detect activity in other neurons within the pacemaker that regulate rapid breathing and sniffing, says Dr. Kevin Yackle, now a faculty fellow at the University of California, San Francisco, who, as a graduate researcher at Stanford, led the study.

The disabled neurons would then alert the brain that something potentially worrisome was going on with the mouse since it was sniffing, and the brain should start ramping up the machinery of worry and panic. So a few tentative sniffs could result in a state of anxiety that, in a rapid feedback loop, would make the animal sniff more and become increasingly anxious. . . .

The implication of this work, both Dr. Krasnow and Dr. Yackle say, is that taking deep breaths is calming because it does not activate the neurons that communicate with the brain’s arousal center. . . .

This is all super-cool. The thing I don’t get is how this relates to deep breathing having a calming effect. The cells that caused sighing had other effects too, and if you knock them out, the mice are more calm: I get that. Or, I should say, I’ll assume that’s correct. But how to you get from there to “taking deep breaths is calming because it does not activate the neurons that communicate with the brain’s arousal center.” I just don’t see it.

I also found this press release on the study but this didn’t clarify thing easier.

The point of this post is not to try to shoot down the study or the news report, just to express my puzzlement. If the topic were social science, I think I’d have a better idea of the steps of reasoning underlying these claims and the strength of the evidence behind them.