It also found that the happily-married couples scored consistently lower on blood pressure tests than those living alone, even if they had a rich circle of friends. Single adults and unhappily married couples also tended to have higher blood pressure during the night, which indicates an increased risk of cardiovascular problems, the study added. Prof Julianne Holt-Lunstad, who led the study for Utah's Brigham Young University, said, ''It's not just being married that benefits health. What's really the most protective of health is having a happy marriage. It's the quality of the marriage, not the marriage per se.'' Spouses often promote healthy habits to their partners, such as encouraging each other to see a doctor or to eat healthily. They also give each other emotional support in stressful times, which may not be so readily available in a bad marriage or for single people, she added.