Researchers in Alberta Canada discover that stress is contagious, and that social support may help buffer these effects, but only for women.
Last year Americans reported their highest stress levels in over a decade according to an American Psychological Association survey. Emotion researchers have long known that feelings like joy, sadness, and anger are “contagious.” Could this also be true for stress? A team at the Cumming School of Medicine’s Hotchkiss Brain Institute at the University of Calgary decided to find out.
How brains respond to other's stress
Their study, published in the journal Nature Neuroscience, looked at whether transmitted stress could impact the brain in the same way that first-hand stress does. In order to answer that question, researchers examined the effects of stress on pairs of male and female mice.
One mouse from each pair was removed and exposed to a mild stressor then returned to its partner. The team then examined each mouse’s corticotropin releasing hormone (CRH) neurons — brain cells that organize our responses to stress. Remarkably, the brain cells in both members of the pair responded identically as if each had experienced the stressor, suggesting that stress may be contagious at a neural level.
To look at how that stress transfer occurs, the researchers used an optogenetic method — applying or removing light to a particular type of cell to turn it on or off. Previous studies show that the activity of CRH neurons is suppressed when they are exposed to yellow light. This is akin to “turning off” the stress response. Once the light is removed, the cells eventually return to normal functioning, and the cells again respond to incoming environmental threats.
To see whether CRH neurons are linked to a “transfer” of stress between mice, the researchers “turned off” the neurons in one of the partner mice while exposing the other partner to a stressful situation. When reunited, the mouse whose CRH neurons had been “turned off” showed no signs of stress. When they turned the CRH neurons back on, the brains of both mice responded as if they’d just encountered a stressful event even if the stressor was no longer present.
Further investigation revealed that the CRH neurons, when activated, released a chemical signal, or pheromone, that may alert other mice to danger.
"We may 'catch another's physiological stress' "
The authors of this study concluded that transmission of stress signals from one partner to a non-stressed partner, or even multiple partners, may explain a mechanism through which stress becomes contagious.
Although this study was conducted with mice, findings are consistent with prior research in humans where an observer’s stress hormone (salivary cortisol) levels were similar to those of another person who had just completed a socially stressful task. This suggests that we may “catch another’s physiological stress”.
How to stop stress contagion
In addition to examining the transmission of stress between mice, the researchers also looked to see whether social interaction might buffer the effects of stress. To do so, they tested whether the impacts of stress would persist when reuniting male and female pairs of mice in their home cages. Interestingly, only female mice demonstrated behaviors suggesting that their stress levels were eased by the presence of social partner.
This echoes research showing sex differences in the fight-flight-or-freeze response in humans where males were more likely to cope with stress by fighting or fleeing, and females tended to adopt a “tend and befriend” strategy.
To translate these findings to human experience, the authors of the mouse study concluded that the ability to obtain information from a distressed individual is important to ensure not only the survival of an individual, but also of a group. In this respect, the ability to transmit stress is adaptive.
They further speculate that the human ability to “transmit” stress may explain why individuals who have not experienced trauma develop symptoms of PTSD after helping those who have undergone a traumatic event.
Mindfulness practices and social support can
help buffer the effects of stress.
The good news is, we don’t have to be unwitting stress transmitters, or passive recipients of other’s stress. Mindfulness practices like meditation and yoga teach us to become aware of our thoughts, feelings, and behaviors. They can empower us to directly acknowledge and address stressful experiences, and to appreciate and accept other’s actions and emotions as well. What’s more, they allow us to recognize our interconnectedness with others, and the need to care for ourselves when helping those who have experienced a stressful or traumatic event.
One of the easiest ways to identify whether or not you’re experiencing stress is to observe the quality of your breath. If you find it to be shallow, rapid, or concentrated in your upper chest, there is a good chance that your nervous system and brain are responding to your experience of stress. You may also be projecting stress to others.
Try modifying your breathing by inhaling deeply, and exhaling as slowly and comfortably as you are able. With time and a bit of practice you can interrupt this cycle, and bring a bit more relaxation and present-moment awareness to your day.
Not sure? Give this exercise a try.
Toni-Lee Sterley, Dinara Baimoukhametova, Tamás Füzesi, Agnieszka A. Zurek, Nuria Daviu, Neilen P. Rasiah, David Rosenegger, Jaideep S. Bains. Social transmission and buffering of synaptic changes after stress. Nature Neuroscience, 2018; DOI: 10.1038/s41593-017-0044-6