High-quality social science research shows that marriage is associated with a number of health benefits. Studies indicate a strong link between marriage and mental health, in particular depressive symptoms. Marriage can both affect and be affected by psychological well-being, through, for example, greater emotional and social support as well as personal connection.

Alternatively, it may be that less-depressed individuals are more likely to marry and remain married. Thus, to discern the true effect of marriage on mental health, research must account for the possibility of a “selection effect.” One method that addresses this selection problem analyzes data collected on the same people over an extended period of time—i.e., longitudinal data. This type of research compares changes in metal health over time of married and unmarried individuals or measures changes in psychological well-being before and after marriage or divorce.

Reviewing a number of such rigorous studies, the Department of Health and Human Services (HHS) concludes:

The current research suggests that marriage—particularly transitions into and out of marriage—affects depressive symptoms for both men and women. In particular, marital entry decreases depressive symptoms, while marital dissolution increases them. Studies suggest that increases in depressive symptoms after divorce are long-lasting and that the prevalence of these symptoms remains elevated years after the marital breakup. In addition, studies that compared the mental health of stably married adults to those who are stably unmarried find that those who remain stably married have fewer depressive symptoms (and smaller increases in these symptoms over time) than do similar adults who remain stably unmarried—even after controlling baseline mental health.

In regard to the selection effect, HHS finds:

Studies based on national data find little evidence that those with fewer depressive symptoms are more likely to marry, suggesting that studies comparing the depressive symptoms of the stably married to the stably unmarried should produce reasonable estimates of the effect of marriage on depressive symptoms.

National trends show that women in general are more likely to experience psychological distress than men. Moreover, according to a team of family scholars led by Professor Brad Wilcox of the University of Virginia, research on the mental health of mothers—all the more important because it affects the well-being of children as well—suggests that “not only are single mothers more likely to be depressed, the consequences of maternal depression for child well-being are greater in single-parent families, probably because single parents have less support and because children in disrupted families have less access to their (nondepressed) other parent.”

For example, the team of scholars cites one study that found that, one year after the births of their children, 29 percent of single mothers who were no longer romantically involved with the fathers reported at least one mental problem, compared to 24 percent of those who were still romantically involved but not living with the fathers, 23 percent of those who were cohabiting but not married, and 16 percent of married mothers. Even when the study accounted for the mothers’ background differences, the mental health disparities remained.

In 2012, as policymakers work to promote Americans’ health, they ought to consider the compelling research evidence on how marriage benefits individuals’ psychological well-being.