New research shows that happily married adults have lower blood pressure than singles with supportive social networks, suggesting marriage may literally be a matter of the heart.

Brigham Young University professor Julianne Holt-Lunstad found that men and women in happy marriages scored four points lower on 24-hour blood pressure than single adults. Having a network of supportive friends did not translate into improved blood pressure for singles or unhappily marrieds, which surprised Holt-Lunstad and her two student collaborators.

“There seem to be some unique health benefits from marriage,” said Holt-Lunstad, whose findings will be published March 20 in the Annals of Behavioral Medicine. “It’s not just being married that benefits health - what’s really the most protective of health is having a happy marriage.”

The study also found, unsurprisingly, that unhappily married adults have higher blood pressure than both happily married and single adults.

Holt-Lunstad, a psychologist who studies relationships and health, arranged for 204 married and 99 single adults to wear portable blood pressure monitors, mostly concealed by their clothes, for 24 hours.

The monitors recorded blood pressure at random intervals throughout the day – even while participants slept. Each participant’s blood pressure level was recorded about 72 times.

“We wanted to capture participants’ blood pressure doing whatever they normally do in everyday life,” Holt-Lunstad said. “Getting one or two readings in a clinic is not really representative of the fluctuations that occur throughout the day.”

All participants completed a roster of friends in their social network and answered questions about the quality of those relationships. Married participants also completed questionnaires on the quality of the relationship with their spouses.

With the monitors recording blood pressure both day and night, the researchers could see that blood pressure for married adults – especially those happily married – dipped more during sleep than happens with singles.

“Research has shown that people whose blood pressure remains high throughout the night are at much greater risk of cardiovascular problems than people whose blood pressure dips,” Holt-Lunstad said.

Holt-Lunstad said that spouses can promote healthy habits, such as encouraging each other to see a doctor and to eat healthy. The marriage relationship is also a source of emotional support in good and bad times. Sharing good news, for example, generates positive emotions, which in turn boosts the body’s functioning.

The study was funded by the Anthony Marchionne Foundation, which supports research on the well-being of the never-married. Funding also came from BYU’s Family Studies Center.

A next step in the research for Holt-Lunstad is to study couples participating in marriage counseling to see if improvement in the marriage translates into improved health.

The two co-authors on the study, Wendy Birmingham and Brandon Jones, worked on the project as undergraduate students at BYU. Jones is now in medical school at George Washington University, while Birmingham is now pursuing a Ph.D. in social psychology with an emphasis in behavioral medicine at the University of Utah.

The study is titled “Is There Something Unique about Marriage? The Relative Impact of Marital Status, Relationship Quality, and Network Social Support on Ambulatory Blood Pressure and Mental Health.”