Bans on same-sex marriage in the United States may be linked to an increase in new HIV infections, according to a new study conducted by economists at Emory University in Atlanta. Researchers estimate that banning same-sex unions raises the domestic HIV rate by four cases per 100,000 people.

“Intolerance is deadly,” said Hugo Mialon, assistant professor of economics at Emory and coauthor of the study alongside fellow Emory researcher Andrew Francis. “Bans on gay marriage codify intolerance, causing more gay people to shift to underground sexual behaviors that carry more risk.”

During the study, researchers used data from the General Social Survey, which has recorded the mindsets of Americans over the past four decades. Findings show that a widespread increase in tolerance toward the gay community from the 1970s to the 1990s cut HIV cases by one per 100,000 people.

“Laws on gay marriage are in flux and under debate,” Francis said in a statement, referring to the recent decision by the California Supreme Court to uphold a ban on same-sex marriage. “It's a hot issue, and we are hoping that policymakers will take our findings into account.”