People who are unhappy in their marriages may have an increased risk of cardiovascular disease, according to a recent study.

Researchers from the University of Pittsburgh found that marriage actually affect the affairs of the heart in ways previously not understood. Unhappy marital interactions have been correlated with thicker carotid arteries and an 8.5 percent greater risk of suffering heart attack or stroke than those with a surfeit of good feelings.

"Growing evidence suggests that the quality and patterns of one's social relationships may be linked with a variety of health outcomes, including heart disease," said Thomas Kamarck, study author and professor of psychology and Biological and Health Program Chair in the University of Pittsburgh Kenneth P. Dietrich School of Arts and Sciences.

For the study, researchers collected data from more than 280 healthy, employed, middle-aged adults who were married or living with a partner in a marital-like relationship. Their interactions were monitored hourly over the course of four days, with the partners rating their interactions as positive or negative.

Carotid artery thickness was also measured.

Researchers found that those partners reporting more negative interactions were found to have thicker carotids.

Nataria Joseph, lead author of the paper, said that these associations could not be accounted for by other behavioral or biological risk factors and were also independent of marital interaction frequency, nonmarital social interaction, or personality factors. The findings were consistent across age, sex, race, and education level.

"These findings may have wider implications. It's another bit of support for the thought that marital or serious romantic relationships play a significant role in overall health. Biological, psychological, and social processes all interact to determine physical health," she said.

Joseph said study does not prove causality, but establishes a strong correlation between unhappy marriages and cardiovascular events.

"What it does show is that health care providers should look at relationships as a point of assessment," Joseph said. "They are likely to promote health or place health at risk."

The findings were recently published in the journal Psychosomatic Medicine.