DNA tests don't cause undue anxiety: study

A Canadian doctor is not surprised by a U.S. study that showed getting a DNA assessment for a variety of diseases didn't inspire people to change their habits by eating better nor exercising more.

"People live in a moment in time. It is difficult to change 365 days of the year," said Dr. Lorne Greenspan, a senior medical consultant at the private Medcan clinic in Toronto.

The study, published Wednesday in the New England Journal of Medicine, surveyed the reactions of nearly 2,000 people about five months after they got the test results. It didn't assess the accuracy of the commercial test used but is the first major study of how people react to commercial genetic testing.

"Time dampens fear," noted Greenspan.

Companies have offered "direct-to-consumer" genetic testing for several years, taking saliva samples from customers, analyzing the DNA and delivering a risk report for a series of diseases.

Critics said the results can be inaccurate, that DNA currently tells too little about an individual's disease risk to be useful and the information might make people unduly anxious.

Greenspan said the results from a DNA test need to be interpreted by a genetic counsellor, Without the counsellor, he said, the results are a mosaic of information.

The DNA test covered 22 conditions, including Alzheimer's disease, diabetes, glaucoma, obesity and cancers of the lung, breast and prostate.

"We don't give consumers enough credit for the fact they can handle this type of information load about themselves," said Dr. Eric Topol, director of the Scripps Translational Science Institute in La Jolla, Calif.

But neither did they cut down on fat in their diets — a common recommendation for several of the conditions tested for — or boost their exercise.

Difficult to change people's habits

"That was very disappointing," Topol said. "Our conclusion is it's very hard to change behaviour."

That might change in the future, when more DNA research will allow companies to identify people at sharply higher risk than they can indicate now, he said.

Only about half the participants said they'd seek medical testing in the future because of their DNA results.

Greenspan said people generally don’t change lifestyles until they get a shock, usually that of a close friend or family member dying suddenly.

"People have to suffer for it to matter to them."

The study was financed by the U.S. government and by Scripps Health, a private health-care organization. Because of stipends provided by the researchers, study participants on average paid less than $250 for the Navigenics Inc. test, which cost $2,500.  A similar test in Canada at Medcan, with a doctor interview and counselling on the results, costs $1,500.

Experts unconnected with the work praised the study.

"They've made an important contribution here," said Dr. Robert C. Green of Boston University, who studies how people react to their genetic risks.

Green said the new work addresses some contentious questions about DNA testing. It shows that on average there was no increase in anxiety, for example, and no costly mass stampede to get medical testing by people with only a modest increase in disease risk.

The researchers said the sample doesn't reflect the general population, but rather those who order DNA tests from companies. They are likely to have higher levels of education and socio-economic standing than the general population and be focused on improving their health, Green said.