A study suggests that being rejected in social situations can do more than cause hurt feelings; it may actually increase inflammation and make you sick.

Researchers at the University of California at Los Angeles have found that rejection increases the same inflammatory proteins that drive conditions like rheumatoid arthritis, asthma, depression, cardiovascular disease and some types of cancer.

“Usually you see increases in inflammatory activity due to physical injury. If you have a cut in the arm you see increases in inflammatory activity and that’s very adaptive because that response can help fight off pathogens and reduce the likelihood of infection,” says study author George M. Slavich, PhD, a postdoctoral fellow at the UCLA Cousins Center for Psychoneuroimmunology. “It’s interesting that you can get increases in inflammatory activity by exposure to social stressors.”

The study, published online in the Proceedings of the National Academy of Sciences involved 124 healthy participants who were put through two potentially stressful social situations: First, the volunteers were brought into a lab and given five minutes to prepare a speech and five minutes to deliver it. Then they were asked to count backwards from 2,935 by increments of seven or 13.  

During the public speaking tasks, two researchers dressed “officially” in lab coats expressed frustration and disapproval at participants’ speed and ability.

Before and after the public speaking tests, oral swabs were taken to measure levels of inflammation while they were exposed to these social stressors. Researchers looked for increases in two inflammatory markers – tumor necrosis factor alpha, or TNF-alpha, and interleukin-6.

During the second part of the study, participants were given MRI brain scans while they played a computerized game of catch.

Though they were actually playing against the computer, they were led to believe that they were playing against other people.

Halfway through the game, the computer dropped the participant from the game of catch in an attempt to create a feeling of social rejection.

Researchers then studied the brain scans to assess neural activity during those moments of social rejection.

What scientists found was that the participants who were dropped from the game had more activity in brain areas related to stress and rejection. They also experienced larger increases in their inflammatory markers.