Apparently. Here’s the press release about this new Economic Journal paper:
The prevalence of the sexually transmitted infection syphilis has fallen by nearly a half in parts of continental Europe as a result of recently introduced national laws that allow for the legal recognition of same-sex partnerships. That is the central finding of new research by Professor Thomas Dee.
How might these laws have influenced the prevalence of sexually transmitted diseases such as syphilis? Professor Dee conjectures that the legal recognition of same-sex partnerships may reduce the levels of sexual promiscuity among homosexuals by creating legal and financial incentives as well as social norms similar to those associated with heterosexual relationships.
What’s more, by reducing the social stigma of homosexuality, these laws could limit the transmission of sexually transmitted infections by discouraging furtive, high-risk sexual activity and the ‘closeting’ of sexually active homosexuals in heterosexual relationships.
The study uses World Health Organization (WHO) data on European countries from 1980 to 2003. During this period, nine European nations – Denmark, Norway, Sweden, Iceland, Netherlands, France, Germany, Finland, and Belgium – introduced new laws that allowed same-sex couples to form legally recognised partnerships and, in some countries, marriages.
So that’s interesting. Here’s the author’s home page; here’s an NBER version of the research. The direction of the effect sounds right to me but the size seems implausibly large. Still, I have not read the paper. (I’m on holiday, remember?)