THURSDAY, Nov. 6 (HealthDay News) -- Cancer-screening messages targeted to minorities that take a negative approach -- emphasizing, for instance, that colon cancer is a bigger threat to blacks than whites -- can actually make minorities less likely to be screened, a new study found.

"There have been some other studies that have hinted at the same thing," said study lead author Robert Nicholson, an assistant professor of neurology and psychiatry at St. Louis University School of Medicine.

For the study, Nicholson and his colleagues asked 300 black people to answer questions about their habits of getting screened for colon and rectal cancer, as well as other cancers. The researchers also asked the study participants about their general mistrust of the medical system.

Next, the researchers asked the participants to read one of four news articles about colon cancer that were created especially for the study, and then answer questions about how likely they were to get screened for the disease.

One article stated that colon cancer was an important problem for blacks, while another focused on the fact that colon cancer outcomes were worse for blacks than for whites.

The third article said outcomes for blacks with colon cancer were improving, but not as much as for whites. The fourth article talked about how results for blacks with colon cancer were improving over time.

The participants' most positive response about cancer screening came after they read the article that results for blacks were improving over time. The article most likely to cause a negative response was the one that simply stated the problem -- that blacks are more likely than any other racial group to develop colon cancer.

The article that said outcomes are improving, Nicholson said, "got the most positive response overall regardless of the individual's level of mistrust."

"The positive message seemed to wipe out the differences between high and low mistrust levels," he said.

The results were published in the November issue of the journal Cancer Epidemiology, Biomarkers & Prevention.

Dr. Harvey J. Murff, an assistant professor of medicine at Vanderbilt University School of Medicine, who has done similar research, called the new findings "very interesting and useful."

"One message [about screening for cancer] is not going to be appropriate for all cultures and backgrounds," Murff said. The new findings underscore the need for public health officials who create messages for cancer screenings to frame them in a more positive way to get the desired result, he said.

Health officials who want to persuade more people to get screened for colon cancer could take a page from those who create messages to screen for breast cancer, which often take into account cultural differences, Murff said. Breast cancer screening has improved greatly over the years, he said, adding, "This has not been looked at as well in colon and rectal cancer."

More information

To learn more about colon and rectal cancer, visit the U.S. National Cancer Institute.