Families don't just share holiday feasts this time of year, they may share stress as well, according to new research from the University of Southern California.
Darby Saxbe is an assistant professor of psychology at USC. As part of the study, she monitored levels of a stress hormone called cortisol in families and partners.
She had them regularly take saliva samples and later tested those samples for the hormone.
Saxbe found that when one person’s cortisol levels jumped, that spike quickly spread to others in the family unit – almost like a virus.
"So it looks as though family members literally are influencing each other’s physiological stress levels," she said.
It's unclear how stress travels from one person to another.
Maybe loved-ones pick up on stressed-out facial expressions, tone of voice or body posture and then unconsciously mimic the emotion as an empathy response.
Saxbe says this tendency might have had an evolutionary advantage in the past.
In early humans, for example, if one member of a group was stressed because of a threat, the whole group would read those cues and gear up emotionally to be ready for it.
These days this can lead to bickering and fighting at the dinner table. This holiday season, Saxbe recommends doing your best to cut your stress before you sit down and hope your family does the same.
"Trying to manage stress has implications not just for one's own well being, but for the well being of one's spouse and one's children," she said.