CHICAGO: A bad marriage might literally make you sick. Marital strife and other bad personal relationships can raise your risk of heart disease, researchers reported on Monday.

What it likely boils down to is stress, a well-known contributor to health problems as well as a potential byproduct of troubled relationships, the scientists said.

In a study of 9,011 British civil servants, most of them married, those with the worst close relationships were 34 per cent more likely to have heart attacks or other heart trouble during 12 years of follow-up than those with good relationships. That included partners, close relatives and friends.

The study, in Monday's Archives of Internal Medicine , follows previous research that has linked health problems with being single and having few close relationships. In the new study, researchers focused more on the quality of marriage and other important relationships.

"What we add here is that, 'OK, being married is in general good, but be careful about the kind of person you have married.' The quality of the relationship matters," said lead author Roberto De Vogli, a researcher with University College in London.

De Vogli said his research team is doing tests to see if study participants with bad relationships have any biological evidence of stress that could contribute to heart disease. That includes inflammation and elevated levels of stress hormones.