This paper examines an accumulating modern literature on the health benefits of relationships like marriage. Although much remains to be understood about the physiological channels, we draw the judgment, after looking across many journals and disciplines, that there is persuasive longitudinal evidence for such effects. The size of the health gain from marriage is remarkable. It may be as large as the benefit from giving up smoking.

It's not altogether clear why, but one item the paper rules out is the notion that marriage reduces risky behavior. Even if two men engage in the same risky behavior such as drinking, the married man will live longer and have better health. (Still no luck convincing Mrs. that I can have a motorcycle.) Some of the studies say men gain more; more say there's no difference in the size of the effect.

Another way of looking at it, the paper concludes, is this: People with better social networks get fewer colds.

(h/t: my colleague BR.)