Stress transmitted from others can actually change the brain, scientists at the University of Calgary have found.
In a new paper published in Nature Neuroscience, the authors report the results of research on mice that were exposed to brief electroshocks on their feet and then reunited with a sibling.
Jaideep Bains, professor of Physiology & Pharmacology at the University of Calgary and one of the study authors, said previous research has shown that stress changes the brain and that it can be, in a sense, contagious.
“We thought, if stress causes long-lasting changes in the brain of the person who was stressed, or the mouse, and stress can be transmitted, does the transmitted stress cause the same changes in the brain?” Bains said in an interview Wednesday.
The answer was yes — brain cells in both animals changed to become more responsive to a future threat. “And it’s indistinguishable from the one that had the real stress,” he said. Furthermore, the mouse that received the second-hand stress was in turn able to transmit it to a third mouse.
The findings point to a useful mechanism that helps groups survive. “If individuals live in a group — you can talk about mice or humans — it is a benefit that if one is exposed to a threat, that information can be relayed to the others,” Bains said. “That information isn’t just a one-shot thing. They actually remember this, to say, ‘OK, I’m not going to go down that street because something bad happened.’”
The message from the study is not to avoid distraught people, Bains said. In fact, female mice showed reduced stress loads when they interacted with a partner. (The same was not true of male mice.)
But the authors say their research sheds light on why serious trauma can cause stress in those around you.
“In humans, buffering or consolation behaviour is almost universal, yet our findings suggest that the partner, or consoling individual, may experience long-term synaptic consequences similar to those of the distressed individual,” the authors write. “This may, for example, offer a potential explanation for why individuals who have themselves not experienced a trauma develop PTSD symptoms after learning of the trauma of others.”
In the mice, partners detected the stress of their partners by sniffing alarm pheromones released from the stressed animal’s anal gland. Humans have the advantage of language, but Bains said recent research suggests we also pick up on non-verbal cues.
He pointed to a recent study that found subjects could detect a difference between the sweat of people who had been skydiving and those who had just done regular exercise. And when the skydiving scent was piped into a room at levels people could not consciously detect, “it changed their heart rate and blood pressure and also affected their ability to make decisions,” Bains said.
He said he hopes his group’s findings will lead to further research to explore why people who suffer from social anxiety disorders and from some neurodevelopmental disorders have problems picking up social cues
Source: National Post