Lead author Lisa Jaremka, a post-doctoral fellow in Ohio State University's Institute for Behavioral Medicine Research, and colleagues asked married couples to complete questionnaires about their relationships. The researchers also collected saliva and blood samples to test participants' levels of a key stress-related hormone and numbers of certain immune cells.
Jaremka said the study involved 85 couples who had been married for an average of more than 12 years, who were mostly white and had an average age of 39.
The research focused on attachment anxiety. Those who are on the high end of the attachment anxiety spectrum are excessively concerned about being rejected, have a tendency to constantly seek reassurance that they are loved and are more likely to interpret ambiguous events in a relationship as negative, Jaremka said.
Married partners who were more anxiously attached produced higher levels of cortisol -- a steroid hormone released in response to stress -- and had fewer T cells, an important components of the immune system's defense against infection, than did participants who were less anxiously attached.
"Everyone has these types of concerns now and again in their relationships, but a high level of attachment anxiety refers to people who have these worries fairly constantly in most of their relationships," Jaremka said in a statement.
The study was published in the journal Psychological Science.