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Calgary university study says stress is contagious: 'It changes the brain'

The study used mice to show how someone's stress can impact how you are feeling.

Jaideep Bains and Toni-Lee Sterley at their physiology lab at the University of Calgary.

Genna Buck / Metro

Jaideep Bains and Toni-Lee Sterley at their physiology lab at the University of Calgary.

“Would you stop freaking out? You're freaking me out!”

Does that conversation sound familiar?

If it does, there's a scientific reason for it: Stress is contagious. And not only that, it changes our brains.

That's the conclusion of a new University of Calgary study published in the journal Nature Neuroscience.

Scientists have known for a while that stress can pass from person to person, and that stress can impact brain function, said University of Calgary physiology professor Jaideep Bains. But it wasn't clear if secondhand stress was powerful enough to cause brain changes as well.

Turns out stress from someone else's traumatic event is every bit as mind-altering as the real thing.

The study looked at sibling pairs of mice; one that got to stay in its cosy cage, the other which was taken out and stressed, such as by a very mild shock to its paws – barely enough for a person to feel, but unpleasant for a mouse. More than a hundred mice in all were studied, making researchers quite confident in the power of the results.

Then the stressed mouse was reintroduced to the cage and allowed to “approach, sniff and investigate” its oblivious mate, Bains said. That's enough to transmit a chemical stress signal, called a pheromone, from one mouse to the other.

“It changes the brain of the partner, and it's indistinguishable from the changes induced by stress,” Bains said. Stress changes the way certain brain cells (neurons) communicate with each other in the hypothalamus, the part of the brain that coordinates the body's response to stress and a host of other cues, he explained. The animals' behaviour went back to normal pretty quickly, but the brain changes lasted for a whole day.

Although specific pheromones have never been isolated in humans, there's evidence we do subconsciously communicate with each other by scent, just like mice do, Bains explained.

In a cool twist, the researchers found a phenomenon they weren't originally looking for: Female mice who were allowed to “socialize” with their pals after being stressed recovered in about half the time than those who didn't get to. The same wasn't true of male mice.

As inconvenient as this phenomenon stress contagion is for us today, it has an advantage in the animal kingdom, Bains said.

“When you live in a group, if one individual is exposed to a threat, they tell you, and you're prepared for that.”

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