Every month I get an email bulletin from the Christian Research Association, this was the top story in the latest one:
Marriage is good for your health! A study funded by the US Department of Health and Human Services has looked into a wide range of well-being measures such as the economic status, mental and physical health of adults and their children, and found married people to be healthier. For example, marriage has been shown to reduce alcoholic intake and marijuana use by both men and women. Those who are in stable marriages report having less depressive symptoms than long-term single or divorced people. However, marriage has also been shown to contribute to weight gain for both genders, and a decrease in physical activity. More details can be found here:
I can personally vouch for the weight gain, though my marijuana intake hasn't dropped at all.