Conventional wisdom tells us that stress can make us sick. This seems likely enough, though science hasn’t exactly mapped all the mechanisms that would explain the connection. Now a new study highlights which immune system compounds could be to blame, making it clear that reducing stress could enhance immunity.

Higher levels of inflammatory markers can, over time, lead to all kinds of problems, from heart disease to cancer.

A group of 122 participants filled out questionnaires about their activities over a period of eight days, noting whether their interactions with others were positive or negative. They also took stressful tests in the lab, before and after which their saliva was tested to measure markers of inflammation called cytokines.

The participants’ levels of cytokines, like interleukin-6 (ILK-6), rose after stressful negative events, often arguments or competitive social interactions. They were not elevated after competitive sports games, suggesting that sports may involve a friendlier form of competition, while competitive social interactions are experienced as negative events.

“The message is that the flotsam and jetsam of life predict changes in your underlying biology in ways that cumulatively could have a bad effect on health," said study author Shelley Taylor. "What this tells me is that people should be investing in socially supportive relationships, and they should not court relationships that lead to a great deal of conflict."

Higher levels of inflammatory markers can, over time, lead to all kinds of problems, from heart disease to cancer. "If you aren't wounded, there's no place for them to go, and they're circulating," Taylor said. "It's not like they've gone to the site of a wound and engaged in anti-infection activity."

One remaining question is whether stress causes inflammation, or whether there is a more nuanced the relationship that just that. People who are more stressed-out by nature could develop more inflammation as a result, or it may be that people with more inflammation to begin with could feel more stressed (and have more negative social interactions) in turn.

More research will be needed to understand this fundamental relationship between stress and immunity. While this is being done (and it will no doubt take a few years or decades before we understand it all), de-stressing as much as possible, doing what you can to reduce feelings of stress, is clearly helpful. Exercise, yoga, meditation, and talk therapy are all effective ways to lessen your mental load and calm your body's systems.

The study was carried out by a team at UCLA and published in the Proceedings of the National Academy of Sciences.