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Better off not knowing? The self-fulfilling risks of genetic testing

Better off not knowing? The self-fulfilling risks of genetic testing - Featured Image

Simply knowing you’re at increased genetic risk for an illness can precipitate symptoms of the disease, new research shows.

Researchers from Stanford University’s Department of Psychology ran DNA tests on around 100 adults for two genes associated with obesity – one related to exercise capacity (CREB1), and the other to appetite (FTO rs9939609).

Instead of giving the individuals their actual DNA test results, the researchers randomly told participants they had either “high-risk” or “protective” genotypes.*

In the first experiment, 116 participants were asked to run a treadmill test before and after receiving personalised genetic information on their aerobic exercise capacity.

After being told they had a “high risk” genotype, people exhibited worse cardiorespiratory fitness –poorer metabolic gas exchange (CO2:02) and lower maximum ventilator flow rate compared to baseline, the study found. They also ran a shorter distance before giving up, and also reported feeling more exerted and hotter.

By contrast, individuals who were told they had the protective genotype did not exhibit any significant changes in their treadmill performance compared with baseline.

In the second experiment, 107 participants were given a meal before and after receiving personalised results on the gene linked with appetite.

Those told they had a protective genotype experienced greater satiety at the second meal – measured by self-reported feelings of “fullness” as well as by post-consumption gut peptide physiology (GLP-1 response).

By contrast, participants assigned the “high-risk” genotype experienced no significant changes in post-consumption feelings of fullness or GLP-1 response compared with baseline.

Across both experiments, the size of the effects due to “perceived genetic risk” were sometimes greater than effect sizes associated with actual genetic risk.

A potent mindset

Writing in the journal Nature Human Behaviour this month, the authors warned: “If simply conveying genetic risk information can alter actual risk, clinicians and ethicists should wrestle with appropriate thresholds for when revealing genetic risks is warranted.”

“Receiving genetic risk information has the potential to instil a potent mindset,” they wrote. “Many studies show that providing people with a genetic causal explanation reduces perceived control compared with providing people with an environmental or lifestyle causal account for a range of conditions and situations, including mental illness, maths performance, and obesity.”

The study comes amid an explosion in genetic testing, with genetic risk estimates now available for over 10,000 conditions, according to the authors.

Although the aim of genetic testing may be to motivate patients toward risk-reducing behaviours, its efficacy is dubious. A recent meta-analysis of 18 studies found communicating the genetic risk of disease had no effect on recipients’ motivation to change behavior, or actual engagement in risk-reducing behavior.

Lifestyle and personality

Dr Sarah Edelman (PhD), a Sydney-based clinical psychologist and author of the book Change Your Thinking, said patients who underwent genetic testing needed to be informed that health outcomes were influenced by both genes and lifestyle.

“Whilst we can’t control our genes, we do have control over lifestyle choices,” she said. “When providing test results, genetic counsellors need to focus on the individual’s potential to influence health outcomes and to frame it in terms of how they can make a difference. For example, saying things like: ‘when people do regular exercise and follow [the prescribed] eating guidelines, they reduce their risk by 30%.’”

Personality also plays a role in how people responded to knowing their personal genetic risk, she said.

“For some people, knowing their genetic risk will be a motivator; for others, it will have the opposite effect. For people who don’t believe they can make a difference to the things that happen to them (low self-efficacy), discovering that they have a high genetic risk for a particular condition may reinforce feelings of hopelessness, and may be unhelpful.”

*The researchers noted ethical challenges in their study design – notably, that some participants were falsely informed of their genotype. It was for this reason that the researchers chose to focus on the effects of genetic risk information for obesity, rather than a more emotionally charged disease such as Alzheimer’s or cancer. They also limited the time under which participants would hold a potentially false belief about their genetic risk to around 1 hour, while under clinical supervision.