After getting into numerous arguments with her husband, Katelyn Capparuccini began feeling consistently unwell. By taking part in an Ohio State University study exploring the relationship between marital disagreements and health, the results of which were published Wednesday in the journal Psychoneuroendocrinology, an explanation for her ill feelings emerged. The scientists behind the study discovered that Capparuccini’s feelings of sickly unease weren’t just in her head. Fighting with her spouse really did make her physically unwell.

The team found that couples whose fights are particularly hostile — think biting criticism and rolling eyes — are more likely to suffer from a condition called “leaky gut.” In this little-understood condition, the lining of the intestines becomes weak and allows partially digested food and bacteria to leak out into the bloodstream. At its worst, leaky gut can mean cracks or holes in the intestinal lining. Marital distress, the researchers write in the study, can cause these dramatic changes in the gut and potentially drive disease-causing inflammation and contribute to poor mental health.

“The inside of the intestine contains trillions of bacteria, in addition to partially digested food,” explains study co-author and Ohio State University professor Michael Bailey, Ph.D., to Inverse. “These bacteria stay inside the intestines as long as the lining of the intestine, commonly referred to as the gut barrier, is intact. The immune system does not strongly respond to these microbes when they are inside the intestine, but if the barrier becomes leaky, then the bacteria, or pieces of the bacteria, can enter into the blood to stimulate an immune response.”

Intestines
Microbes within an intestinal wall. 

Bailey and his colleagues wanted to know how marital strife affects physiology, so they recruited 43 married couples, in which individuals ranged in age from 24 to 61 and had been married for at least three years, and let them fight it out. In the study, the researchers asked the couples about their relationship, suggested that they should talk about the most difficult aspects of being together, and then left the room. Left alone, the couples fought — sometimes about in-laws and most often about money. All the while, the arguments were videotaped, which would later serve as visual evidence of how hostile the fights became.

Importantly, the researchers also took blood samples from the participants before and after the arguments. These revealed that the couples who demonstrated hostile behaviors were more likely to have a biomarker for leaky gut called LPS-binding protein, which essentially indicates the presence of bacteria in the blood. People with high levels of this protein in their blood also had higher levels of a C-reactive protein, a primary biomarker of inflammation.

Bailey says nobody really knows yet why hostile behavior correlates with higher levels of LPS-binding protein, but he reasons that “more hostile behaviors could involve a stronger bodily response to the marital conflict that leads to the leaky gut, and the observed increase in the LPS-binding protein.”

Ultimately, the body’s response is most likely a consequence of potent stress. Previous research, says Bailey, has already established a link between stress, the sympathetic nervous system, and changes in microbes in the gut. Inflammation, meanwhile, can lead to age-related diseases including depression, heart disease, and diabetes. Eating vegetables, whole grains, lean proteins, and healthful fats can help decrease the risk of gut-related inflammation — but marriage counseling might also be what the doctor prescribes.