Science points to a very easy way to be happier, have less stress, reduce your risk of dying from cancer and heart disease, and potentially live longer: Simply get married. Research overwhelmingly shows that married men are both mentally and physically healthier than single guys and, as a result, tend to outlive them.

"The differentials between married and unmarried men are pretty remarkable in terms of overall health and life expectancy," says Susan Brown, co-director of the National Center for Family and Marriage Research at Bowling Green State University in Ohio.

Here's the proof: Last year, Harvard University researchers found that married people were significantly more likely than unwed folks to detect prostate, lung, colorectal, and other forms of cancer in their early stages and to get treatment for the disease. The study also showed that married people were much less likely than singles to die of cancer.

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Similar results have been found for heart disease – the number-one killer of American men. Cardiologists at New York University's Langone Medical Center analyzed data from more than 3.5 million people nationwide and learned that, independent of other cardiovascular risk factors, married people age 50 and younger had a 12 percent less chance of developing any type of vascular disease than their unwed counterparts. Another large study found that men with wives were 46 percent less likely to die of heart disease than single guys – also after taking into consideration diabetes, smoking, blood pressure, obesity, and other major risk factors.

Studies also show that married people are happier and experience less stress – both of which play a big role in maintaining whole-body health. "Stress and depression undermine psychological health, which spills over to physical health," says Brown.

There are a couple of factors at play here. "Marriage is both a cause and a consequence of good health," says Michael Pollard, a sociologist with the RAND Corporation, a nonprofit research organization. "Research shows that healthier people are more likely to get married in first place and less likely to divorce. However, while this is definitely part of the equation, most of these studies suggest that marriage also causes good health and improves overall well-being – especially for men."

So why is marriage such a boon for men's health? It turns out guys, more so than women, rely on their spouses for emotional support and companionship, which leads to improved mental health. "When a woman is down in the dumps, she might call a girlfriend, but a guy will rely on his wife much more than his friends," Brown says.

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Men also benefit from their wives keeping tabs on their physical health. "Women tend to be better than men about encouraging their spouses to maintain healthy behaviors like going to the doctor and eating healthy foods," Pollard says. "They also discourage risky activities like smoking and heavy drinking."

Of course, the health benefits of marriage can be severely diminished if the relationship isn't solid. Even though much of the research touting marriage's perks hasn't delved into the quality of the relationship, Brown says a contentious, unhappy marriage can undermine both partners' health. But if you're madly in love with your spouse, and you appreciate her care and companionship, you have a pretty great shot at living a long, healthy life.