Will information on risk genes actually change behaviour?

A recent news focus in Science is well worth a read if you're lucky enough to have an institutional subscription. If you don't have a subscription, my post a couple of days ago on the problems with genome-wide association studies covers some of its major points: the article describes the disappointing results from even extremely well-powered genome-wide association studies (in type 2 diabetes, for instance) and lists copy number variation, rare variants, population differences and epistasis as potential explanations.

The article also tackles the fascinating question of whether information on the types of small-effect risk genes identified by recent genome-wide studies is likely to have much of an effect on patient behaviour and disease outcomes.

Two years ago, behavioral epidemiologist Colleen McBride and human geneticist Lawrence Brody [...] offered volunteers in Detroit, Michigan, the chance to learn whether they carried deleterious variants for eight health conditions, including diabetes, colon cancer, and osteoporosis. Because the variants are common, virtually everyone was expected to harbor at least a couple. Those monitoring the study's safety "were really worried, literally, that people were going to jump off bridges" when they learned that their risk of disease was increased, says McBride.

Among the 300 or so who have participated, that hasn't happened--quite the opposite. "They're not having big emotional responses," says McBride. The researchers are tracking the volunteers to see whether the information affects decisions to reduce disease risk, such as seeking out a smoking-cessation program or consulting with a nutritionist.

Behavioral specialists have shifted from worrying about the devastating effects of learning about these new genetic risks to wondering whether the information will make any impression at all.

Patient indifference to genetic risk factors wouldn't come as a huge surprise to any clinician who has ever tried to convince a high-risk patient to cut down on dangerous activities for the sake of their health: smokers keep smoking even though the increased risk of heart and respiratory diseases is well-publicised.

However, it remains an open possibility that obtaining a personalised genetic risk profile will serve as a more effective spur to behaviour changes than generic "smoking is bad" messages from clinicians and public health organisations. The article mentions a study currently in progress to test this possibility in a cohort of smokers with a family history of Crohn's disease (smoking doubles the risk of this disease).

It's amazing that these sorts of studies haven't been done yet, given how important they are: if it turns out that genetic information doesn't reduce risk behaviour in the real world, then the impact on public health of the hundreds of millions of dollars spent on complex disease genetics may actually be very small. I'm hopeful that this won't be the case - but it would be nice to have some actual evidence one way or the other...

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