Don’t mock your coworker’s sunny disposition on Monday mornings. His optimism may be keeping his heart healthier than yours, according to researchers from the Harvard School of Public Health. To determine the power of staying positive, researchers looked at 200 previous studies that measured psychological traits, alongside health behaviors and risk factors for cardiovascular disease. Happiness and optimism were both linked to a lower risk of heart disease and stroke, with the most optimistic people having the greatest benefits. The study, published in the journal Psychological Bulletin, also found that optimistic and happy people tended to have healthier lifestyles. They exercised more, ate better, and slept more. In addition, they were less likely to have risk factors for heart disease and stroke, including high blood pressure, high cholesterol, and obesity. All of this is known to contribute to better heart health. Does being happy or optimistic make the heart healthy, or does a positive attitude just encourage healthy behaviors? The study was not large enough to answer that question, but negative psychological factors—like stress and depression—have already been found to increase the risk of heart attacks. Staying positive, then, may work the other way, such as by lowering blood pressure and cholesterol. Even if you aren’t upbeat all the time don’t let that get you down. Healthy eating and exercise are still an important part of lowering your risk of heart disease and stroke. There are also psychiatric interventions, like behavioral therapy, that can help you find a more positive outlook on life, even when confronted by your overly perky coworkers.