A recent study published in Nature Neuroscience suggests that stress transmitted by others can actually change another person’s brain in the same way as your own anxiety.
We know the stress-related brain changes that underlie many mental illnesses, including PTSD (post-traumatic stress disorder), anxiety disorders, and depression. Recent studies also indicate that stress and emotions can be contagious, but how long does the effect last?
To find out, a team of researchers led by Jaideep Bains of the Hotchkiss Brain Institute (HBI) of the Cumming School of Medicine at the University of Calgary (Canada) recently investigated the effects of stress in male or female mice.
The researchers removed one mouse from each pair for this study and exposed it to mild stress before returning it to their partner. They then examined the responses of a specific population of cells, particularly CRH neurons. The latter control the brain’s response to stress. In each subject, the scientists observed that the networks in the brain of the stressed mouse and the partner were altered in the same way.
“What was remarkable,” says study co-author Toni-Lee Sterley, “is that the CRH neurons of the partners, who themselves were not exposed to real stress, exhibited identical changes to those measured in the stressed mice.
The team then relied on optogenetics, which allows to control a mouse remotely, thanks to an optical fiber emitting light directly into his brain. The goal was to be able to “turn off” or “turn on” the neurons involved during the stress phase. In doing so, they then prevented the changes in the brain that would normally have occurred. When they “silenced” the neurons of the partner during his interaction with the stressed mouse, the stress was not transferred to the partner either.
On the other hand, when the researchers activated these neurons using light in the mouse’s brain, even in the absence of stress, the brain of the mouse receiving the light and that of the partner were changed as they would be after a real stress.
The team has discovered that activation of these CRH neurons causes the release of a chemical signal, an “alarm pheromone” of the mouse that alerts the partner. The partner who detects the signal can in turn alert other members of the group. This propagation of stress signals reveals a key mechanism for the transmission of information, which can be crucial in the formation of social networks in various species.
We do not know yet if the same mechanisms apply to humans, but the researcher suggests that there are good reasons to believe it. “We easily communicate our stress to others, sometimes without even knowing it. The ability to feel the emotional state of another is a key element in creating and building social bonds. ”
The study was published in Nature Neuroscience.