We readily communicate our stress to others, sometimes without even knowing it.
Scientists, including one of Indian origin, have found that stress transmitted from others can change the brain in the same way as a real stress does.
The study, in mice, showed that the effects of stress on the brain are reversed in female mice following a social interaction. This was not true for male mice.
"Brain changes associated with stress underpin many mental illnesses including PTSD, anxiety disorders and depression," said Jaideep Bains from the University of Calgary in Canada.
"Recent studies indicate that stress and emotions can be contagious. Whether this has lasting consequences for the brain is not known," Bains said.
For the study, published in the journal Nature Neuroscience, the researchers studied the effects of stress in pairs of male or female mice.
They removed one mouse from each pair and exposed it to a mild stress before returning it to its partner.
They then examined the responses of a specific population of cells, specifically CRH (Corticotropin releasing hormone) neurons which control the brains response to stress, in each mouse, which revealed that networks in the brains of both the stressed mouse and naive partner were altered in the same way.
"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," said Toni-Lee Sterley from the University of Calgary.
The researchers discovered that the activation of these CRH neurons causes the release of a chemical signal, an alarm pheromone, from the mouse that alerts the partner.
The partner who detects the signal can in turn alert additional members of the group.
This propagation of stress signals reveals a key mechanism for transmission of information that may be critical in the formation of social networks in various species.
The researchers suggested that these findings may also be present in humans.
"We readily communicate our stress to others, sometimes without even knowing it. There is even evidence that some symptoms of stress can persist in family and loved ones of individuals who suffer from PTSD," Bains said.
"On the flip side, the ability to sense another's emotional state is a key part of creating and building social bonds," he added.