If your roommate or significant other has been in a bit of a tizzy recently, you might be the unfortunate bearer of some of their stress. A new paper published in Nature Neuroscience found that mice can catch stress from their partners. The researchers believe the same mechanism may apply to humans as well.
Jaideep Bains led a team at the Cumming School of Medicine's Hotchkiss Brain Institute (HBI) at the University of Calgary to determine the effect a mouse’s stress had on their partner. First, they separated the mice from one another. Then, they exposed one from each pair to a form of mild stress.
The team analyzed the corticotropin-releasing hormone (CRH) neurons of both mice to determine the animals’ stress levels. Interestingly, the brain patterns in both mice were changed in the same way, indicating both were stressed whether or not they had been exposed. This suggests the so-called naïve mouse had “caught” anxiety from the stressed mouse.
"What was remarkable was that CRH neurons from the partners, who were not themselves exposed to an actual stress, showed changes that were identical to those we measured in the stressed mice," Toni-Lee Sterley, a postdoctoral associate involved in the study, explained in a statement.
The team followed up the experiment with a second, using an optogenetics approach that allowed them to turn the neurons “on and off” with light. Turning them off blocked the brain’s response to stress that would otherwise take place. Blocking the brain’s response to stress in the pre-exposed mouse prevented the stress from passing on to the naïve mouse. Reactivating the neurons in one mouse resulted in stress in both mice.
The researchers found that it came down to a chemical signal (or “alarm pheromone”) that acts as a warning to other members of the group, kind of like a social defense mechanism.
This might sound airy-fairy, but the scientists point out that this supports pre-existing research. "Recent studies indicate that stress and emotions can be 'contagious'. Whether this has lasting consequences for the brain is not known," said Bains.
We do not know yet if the same mechanisms apply to humans as they do with mice, but Bains says there are good reasons to believe they do.
"We readily communicate our stress to others, sometimes without even knowing it,” Bains said in a statement. “There is even evidence that some symptoms of stress can persist in family and loved ones of individuals who suffer from PTSD. On the flip side, the ability to sense another's emotional state is a key part of creating and building social bonds."