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Behavior and Genetic Risk

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As a health psychologist at King's College, London, who studies people's responses to genetic test results, Theresa Marteau says that just informing people about their genetic risk often won't motivate them to change their lifestyle. Genome Technology's  Ciara Curtin recently spoke with Marteau about her work. What follows is an excerpt of their conversation, edited for space.

Genome Technology: One of the tenets of personalized medicine is that knowing a person's genetic predispositions will lead to earlier interventions. Do you think that will be the case?

Theresa Marteau: First, whether or not there is evidence that an early intervention, if engaged in, will reduce risk — that link isn't always there. If one does have that link, whether or not people will engage in the behavior itself or engage with that intervention to reduce their risk, I think it is difficult to say because there have been too few studies to have enormous confidence. The pattern of evidence would not lead one to be optimistic that people are going to respond to genetic risk information in any way that is different to other kinds of risk information. In the main, we know that giving people information about their risks is most often not sufficient for them to engage in behavior change.

GT: You are currently working on a study on how people react to knowing their risk for Crohn's disease, and how smoking affects that risk. How do people respond to that information?

TM: We are interested in learning whether or not assessing risk using DNA affects people's motivation, for better or worse. One [theory] is that if you [know the results of a] genetic test, people start to feel fatalistic. The other hypothesis is that people may respond to genetic information in a more positive way because it is novel information and it is personal. And so that may serve to increase motivation to reduce the risk identified using DNA.

What we are able to do in this trial is assess the likelihood that these individuals will develop Crohn's disease and give them the information and support to halve their risk by stopping smoking. In half [of the study population who are first-degree relatives of people with Crohn's disease], the risk is assessed using DNA, family history, and smoking status. For the other half, the risk is assessed using family history and smoking status. This study is particularly relevant to the current debates about personalized genetic testing [since] Crohn's disease is a condition where the genes are important, but actually they account for relatively small amounts of variation. For those that have none of the risk-conferring mutations, the chances they will develop Crohn's disease is four percent, which can be halved if they stop smoking. A sub-question is: are people motivated to reduce their risk from four percent to two percent?

GT: What utility do you think consumer genomics companies will have?

TM: Commercial testing, if people want to buy it, then that's fine — I'd say there's a market for it. The key thing is, in the healthcare systems one does need to demonstrate that this is providing a benefit.