Same-Sex Marriage Legalization and Sexually Transmitted Infections Across Europe

I examine how same-sex marriage laws affect sexually transmitted infection (STI) rates, using country-level panel data from Europe. Dynamic difference-in-differences models show that same-sex marriage laws decrease the spread of shorter-term (syphilis, gonorrhoea) and longer-term infections (HIV, AIDS) among the general population. These effects are persistent over time and are much stronger than other same-sex relationship recognition policies. Further investigation reveals significant heterogeneity; same-sex marriage laws lead to sizeable decreases in all STIs among the most at-risk population for an infection, men who have sex with men, with additional positive externalities on the health capital of heterosexual men and women.