When a newly married couple smiles, everyone knows why. When a ten-year married couple smiles, everyone wonders why. Despite all the jokes about miserable marriages, research suggests that people who are married are happier and healthier. But, are these people happier and healthier because they are married? On the Harvard Health Blog , Dr. Robert H. Shmerling reports there are four prominent theories about this. First, people in happy marriages may be healthier because they have lower levels of