The evidence is unequivocal that being married is correlated with happiness. The evidence is also unequivocal that the causal direction goes both ways. That is, having a strong marriage may make us happy, but those of us who are happy to begin with appear to be more likely to attract a marriage partner and to erect an enduring and fulfilling partnership. For one example of a study in this area, researchers tracked the happiness of over 10,000 individuals over the course of 5 years (from the late 1980s to the early 1990s) and found that those in the sample who were married (and especially married for the first time rather than remarried) were significantly happier than any other category (i.e., single, divorced, cohabiting, etc.). Looking at shifts in people's marital status over the course of the study (e.g., from single to married, or from married to divorced) revealed that those who remained married through the 5-year period were happier and less depressed than those who become divorced, those who became separated, or those who remained divorced, separated, or single. Thus, being married and staying married is clearly associated with greater happiness. However, quite a few investigations have persuasively shown that it is happiness that leads to marriage, as opposed to the reverse. In one of my favorite studies, for example, women who expressed authentic happiness in their college yearbook photos, taken at ages 20 or 21, were relatively more likely to be married by age 27 and less likely to still be single at age 43.
Another possible and vital correlate—or perhaps consequence—of marriage is good physical health. A growing number of studies are showing that married people are relatively less likely than other groups to have high blood pressure, to develop heart disease or cancer, to have surgery, to come down with pneumonia, to succumb to dementia, to get into a car accident, and even to be murdered. Married people—but especially those who stay married to the same person for as many years as possible—live relatively longer.
It would be irresponsible of me not to bring up some crucial caveats to such findings. First, researchers have shown that being married leads people to report that they are happier with their lives in general (in part because the question itself probably compels them to weigh the fact of being married as signifying greater happiness), but being married does not necessarily lead people to experience more happiness moment to moment. For example, a study that tracked how married women occupy their time during every hour of the day found that marriage confers both benefits and costs to women, and that these benefits and costs appear to offset one another. So, married women spend less time alone than their unmarried peers and more time having sex, but they also spend less time with friends, less time reading or watching TV, and more time doing chores, preparing food, and tending to children.
Another caveat is that, as Bella DePaulo has persuasively argued, studies of married people are systematically biased by the fact that any participants whom researchers recruit who are currently still married must already be on the happy side, as the less happy among the married—up to 40% or more in Western nations—would presumably have already been separated or divorced. That's like doing a study in which anyone who doesn't confirm our hypothesis (in this case, that hypothesis is that married people are better off) ends up dropping out, thus skewing our results.
Finally, it turns out that although marriage does offer people a substantial happiness boost, that boost is biggest right after the engagement and tends to dissipate after a few years. (How many years? Two on average, according to one study.)
These findings may seem confusing. What's the bottom line—does marriage contribute to our happiness (and our health) or does it not? Scientists have concluded that strong, warm, fulfilling interpersonal relationships undoubtedly make us happy. An avalanche of research demonstrates this. Note, however, that this conclusion encompasses all kinds of close relationships, not marital relationships per se. Both the literatures on marriage and health and on marriage and happiness indicate that the key relationship doesn't have to be a sexual one or one that involves a honeymoon or a stroll down the aisle.
So, does marriage make us happy? Yes, but so does a lifelong bond with a friend or sibling. Should marriage make us happy? That is much more difficult to answer. Having a spouse confers many potential goods on us—children, intimacy, having a party date, domestic and financial support, companionship in our old age—and happiness is only one of them