Craigslist sex cruising linked to more HIV

Study finds infection rate jumped 15.9% once website entered markets

MINNEAPOLIS — Cruising for sex on Craigslist personal ads resulted in a 15.9 percent increase in HIV infections after the website entered various U.S. markets, according to a study by the University of Minnesota published in MIS Quarterly.

The study estimates that the Craigslist effect led to about 6,000 additional HIV cases a year from 1999 to 2008 in the 33 states studied, and additional treatment costs of $62 million to $65.3 million.

Jason Chan, an assistant professor of information and decision sciences, said he got the idea for the study several years ago while working on his doctorate at New York University. Chan’s dissertation focused on the social and health effects of Internet platforms. In the course of his studies, he read about a doctor who traced sexually transmitted diseases to online chat rooms.

“I went to Craigslist in New York and went through the ads. To my shock, I found out almost all the ads were hookup ads. They were very explicit,” said Chan, who wrote the journal article with professor Anindya Ghose of NYU.

The econometric method used by Chan and Ghose has the equivalent effect of comparing HIV trends across markets with and without Craigslist, and before and after Craigslist exists in these locations.

They also compared the HIV rate against the number of personal ads in contrast to the number of escort ads placed in a separate Craigslist section for professional services.

The study found that HIV incidence began to increase about a year after Craigslist entered a market, then climbed through the study period. Chan said the one-year delay makes sense, because it takes time for the ads to reach a critical mass and for those infected to seek help.

The association between Craigslist and HIV occurred only with respect to personal ads — not professional escort services. Chan figures that sex workers took more precautions than people seeking sex in a social context.

Craigslist has since dropped the professional escorts ads, so it’s possible that those have moved surreptitiously into the personal ads.