ABC News' Mara Schiavocampo and Nikki Battiste report:
Does simply watching super-stressful situations make you uncomfortable?
A team at Saint Louis University recently created "secondhand stress" to study whether it could be as contagious as a cold. They had stranger observing a man nearby who was defending himself against a false accusation. The question: Would the stranger catch the accused man's stress?
After measuring strangers' heart rates and cortisol levels, the researchers found that a person could catch another person's stress, even if they had never met.
"To find that in some people, some of the time, you can elicit these responses just by sitting and watching someone else under stress was somewhat surprising to us," said Tony Buchanan, associate professor in the Department of Psychology at Saint Louis University.
Researchers said that stress can be passed on through things like facial expressions, voice frequency, odor and touch, and that it's often not good for you.
Over time, chronic stress can increase the risk of heart attack, stroke and depression.
And while a person can catch stress from a stranger, studies have shown that you are four times more likely to get it from someone you know - between coworkers, friends and even loved ones.
In a potentially anxiety-inducing experiment, researchers at the University of California, San Francisco, attached cardiovascular sensors to the hearts of mothers who were told to give an impromptu speech while evaluators scowled critically. The sensors measured the mothers' heart rate and other indicators for stress.
After the mothers were finally reunited with their children, playing happily in another room, the children were hooked up to sensors too.
All of the babies of the stressed mothers had an equally elevated heart rate, showing they had caught their mothers' stress.
One child even appeared uncomfortable with the evaluator who had been mean to the mother.
"The baby was able to pick up on that and translate it into social behavior," said Sara Waters, a postdoctoral fellow and lead researcher at UCSF.
The greater the mothers' stress, the greater the babies' and researchers say that's true with strangers as well.
"By knowing how this happens, we can start being mindful of both what we're putting out, but also how people around us are affecting us," Waters said.