Looking for medical information on Internet message boards can be risky for consumers. Some of it is confusing, misleading or downright wrong. But for medical researchers, all that chatter can yield some valuable insights.

Scientists from the University of Pennsylvania, for example, are mining message boards and Twitter feeds to see what breast-cancer and prostate-cancer patients are saying about herbal and nutritional supplements—including whether they take them and why and what side effects they encounter.

"People are often hesitant to talk to their doctors about herbs and supplements. But they do talk with other people, especially in an anonymous setting like a discussion board," says principal investigator John Holmes, an epidemiologist and medical-information specialist. Even if there is no scientific evidence to support what people post, he says, "it's useful to identify areas that would merit further study with all scientific rigor."

Businesses have been monitoring the Internet almost since its inception for intelligence on what people say about their products or rivals'. Mining for medical information is newer but growing rapidly. Gunther Eysenbach, a University of Toronto professor who founded the Journal of Medical Internet Research in 1999, says he used to worry about the gap between evidence-based medicine and what people post—until he realized that the Internet can be a great source for information epidemiology, or what he calls "infodemiology." By monitoring discussions about, say, the notion that vaccines cause autism, "we can learn a lot about public sentiment, public attitudes and public knowledge," he says.

Early Warning Signs

Chatter on the Web also can serve as an early warning sign of adverse events linked to drugs or medical devices. "We see patient conversations on the Internet as the largest post-marketing study ever," says Michele Bennett, chief operating officer of Wool Labs, a business-intelligence company founded in 2007. The Wayne, Pa., firm can search the entire Internet for conversations that shed light on patient beliefs, buying patterns or decision making—whatever its clients, many of them drug companies, are seeking.