If medical scientists sometimes find it hard to recruit enough volunteers–especially Blacks–to participate in research studies, there may be a good reason, a new University of North Carolina at Chapel Hill study shows. A surprisingly high percentage of Americans surveyed–almost 80 percent of Blacks and 52 percent of Whites–were suspicious that they might be used as “guinea pigs” without their consent.

The first-of-its-kind study, conducted by a UNC School of Medicine investigator and colleagues, relied on data gathered in 1997 through a national telephone survey of 909 people sponsored by the Institute for Minority Health Research at Emory University. It showed that even after controlling for social and economic factors, Whites were not very trusting of doctors, and Blacks were even less so.

“Distrust has been proposed as one of the barriers to participation by minorities in research, but until now there haven’t been any studies to show how big that distrust might be or to substantiate racial differences,” says Dr. Giselle Corbie-Smith, assistant professor of social medicine and medicine at UNC. “For that reason, we tapped an existing database to see if there were differences by race and what might account for them.

“We found that in general, both Blacks and Whites distrusted medicine and medical research, but Blacks were significantly more likely to have high levels of distrust,” Corbie-Smith says. “Those differences didn’t go away when we controlled for factors that might influence them such as income and education.”

A report on the findings appeared in the Nov. 26 issue of the Archives of Internal Medicine, a journal published by the American Medical Association.

Specifically, Corbie-Smith and her colleagues found that 41.7 percent of Blacks and 23.4 percent of Whites did not trust their doctors to explain research participation fully. Almost 46 percent of Blacks and almost 35 percent of Whites felt their doctors exposed them to unnecessary risks when deciding on treatment.