From Iron Knee at Political Irony:
Two years ago, the Supreme Court struck down laws against same-sex marriage as unconstitutional. Before that ruling, 36 states (plus the District of Columbia and Guam) already issued marriage licenses to same-sex couples. This disparity allowed scientists to study the effects of the change, and the results showed an interesting benefit.
Researchers at Johns Hopkins compared suicide rates over time in states that legalized gay marriage, with states that did not.