Apr 05, 2015 06:07 PM EDT By Staff Reporter, UniversityHerald Reporter

Craigslist's entry into a market results in a 15.9 percent increase in reported HIV cases, according to a recent study.

Researchers at the University of Minnesota and NYU's Stern School of Business found that when mapped at the national level, more than 6,000 HIV cases annually and treatment costs estimated between $62 million and $65.3 million can be linked to the popular website,

"I actually think that the creators of Craigslist had no intent of harming society. They came in with good intentions," Jason Chan, assistant professor of Information and Decision Sciences at the Carlson School of Management, said in a statement. "At the same time, they did not anticipate that users could use the features in an unexpected way with unintended consequences."

For the study, Chan and Professor Anindya Ghose analyzed data in 33 states from 1999 to 2008. Because Craigslist randomly enters individual markets with respect to HIV trends, it provided a unique natural experiment setup from which the researchers could uncover the connection.

After conducting a series of tests to eliminate other possible causes that might be driving the HIV trends such as increased testing in a community, the researchers discovered that the upward shift was influenced by ads in Craigslist's personals sections, not the site's escort service ads. This finding was in line with existing research that shows internet-facilitated sex workers are less likely to participate in risky sexual practices with clients.

"Our study results suggest that there is a new social route of HIV transmission that is taking place in this digital era," Chan said. "Health care practitioners and policymakers have to look more closely at online platforms to assess how its usage may facilitate the spread of HIV and STDs across the country."

These findings provide strong evidence, using data from animal models and humans, that exposure to pyrethroid pesticides, including deltamethrin, may be a risk factor for ADHD, according to Jason Richardson, lead author of the study.

The findings are detailed in the December issue of MIS Quarterly.

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