When the U.S. Supreme Court ruled in June in favor of same-sex marriage, the decision was hailed by most people as a victory for civil rights. Lost in that debate, however, was another consideration: public health.

It’s often said that social policy is also health policy. Mark L. Hatzenbuehler, a psychologist at Columbia University, knows the expression all too well. His job is to back up that argument with science, and in the last few years his research has found that same-sex marriage laws have a significant effect on the health of lesbian, gay and bisexual (LGB) individuals.

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A 2010 study by Hatzenbuehler, conducted under the aegis of the National Institutes of Health and published in the American Journal of Public Health, found that LGB individuals who lived in states that had banned same-sex marriage suffered from psychiatric disorders significantly more often than those who lived in states that were neutral or allowed them to marry. How significant? The findings revealed:

  • a 37 percent increase in mood disorders;
  • a 42 percent increase in alcohol-use disorders; and
  • a 248 percent increase in generalized anxiety disorders.

The study was based on data from more than 34,000 people who were already part of another large National Institutes of Health study that had begun in 2004. That’s also around the time that states started banning same-sex marriage, so Hatzenbuehler and his team conducted follow-up interviews asking how the mental health of lesbians, gays and bisexuals had been affected by the bans.

Alternatively, in another study, Hatzenbuehler looked at the effects of same-sex marriage when Massachusetts became the first state to legalize it in 2004. He found that in the 12 months following the law’s passage, there was a 13 percent reduction in health-care visits and a 14 percent reduction in health-care costs among gay and bisexual men. A look at the diagnostic codes used in their treatments also revealed fewer diagnoses of stress-related health problems like hypertension, depression and adjustment disorders.

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In the 2010 study, Hatzenbuehler and his colleagues surmise that the reason same-sex marriage bans correlate with mental health issues may be that “creating constitutional amendments banning gay marriage reinforced the marginalized and socially devalued status of LGB individuals. Moreover, the negative political campaigns against gays and lesbians by proponents of these amendments, which were well circulated in the media, further promulgated the stigma associated with homosexuality.” The bottom line, the study’s authors wrote, is that “living in states with discriminatory policies may have pernicious consequences for the mental health of LGB populations. These findings lend scientific support to recent efforts to overturn these policies.”

Hatzenbuehler says that he and his colleagues came to this conclusion not as political activists but as scientists. Hatzenbuehler’s past research has looked at the health consequences of other policies as well. “As a social scientist, I think we have a role to play in these debates,” he says. “I think we can point out the health consequences of certain policies, and I hope my work contributes to this debate.”

It already has. The Massachusetts Office of the Attorney General cited his research in an amicus brief it filed in the 9th U.S. Circuit Court of Appeals on behalf of Hollingsworth v. Perry, one of the cases the Supreme Court decided in June. Along with its arguments based on civil rights, discrimination and the affects on children, the brief states that, “It is in a state’s interest to protect its residents from the harms of discrimination and social stigma. … Inequality under the law can lead to both, which can cause significant public health problems.”