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How DNA Test Results Can Change People's Behavior And Physiology

Between 2015 and 2018, sales of DNA test kits boomed in the United States and allowed websites to build a critical mass of DNA profiles. The four DNA websites that offer match services — Ancestry, 23andMe, Family Tree DNA, My Heritage — today have so many users that it is rare for someone not to find at least one distant relative. (Eric Baradat/AFP/Getty Images)

As DNA testing becomes more sophisticated — and widely available — consumers have new access to all kinds of genetic information, from whether they're likely to sneeze when exposed to sunlight to whether they carry the BRCA genes that increase the risk of breast cancer.

Some of that information is having a positive — maybe even life-saving — impact on people. But two researchers at Stanford University wondered, what if knowing you had certain genetic material led to you creating a mindset about your capabilities, or even a physiological reaction?

Alia Crum and Bradley Turnwald set out to test this hypothesis, gathering 200 volunteers and briefly giving them false information about whether they had a gene that either limited their ability to exercise, or made them more hungry.

"What we saw was that, regardless of people's actual genetic risk, what really mattered was what we told them," Turnwald tells Here & Now's Robin Young.

Interview Highlights

On deciding to pursue this topic in their research

Bradley Turnwald: "Well obviously, more and more people are getting genetic risk results, and you can get them in the privacy of your own home. Prior research has looked at whether there are emotional effects of receiving this information, are there behavioral effects on people after receiving this information. But we really wanted to know, does merely receiving this information change or actual risk by changing your mindset, and can that even influence the way your body responds?"

"Our genetic makeup is just one piece of the puzzle. Our mindsets are another piece — an often-overlooked piece."

Alia Crum

On how the diet portion of the study worked

Alia Crum: "We had [participants] come in for a baseline session, which means we had their baseline levels in terms of their gut peptides or their hormones in response to what they ate in the diet study, and also in terms of their oxygen conversion rates in the exercise study. And then we had them come in a week later. Some were told they were at risk. Some were told they were protected.

"Of the group who had the genetically at-risk profile, half were told they were at risk and half were told they were protected. And of the people who were protected, same thing: Half were told they're at risk, and half were told they were protected."

On how participants fared after being told they were at risk

Turnwald: "Across the board, people who were told that they had an increased genetic risk for exercise capacity, they performed worse, and people who said that ... they were protected genetically from this poor exercise capacity, they performed at similar levels as their baseline. And so we really saw the power of that information changing their outcomes."

On physiological changes observed among participants in the diet experiment, after they received information about their genetic makeup

Crum: "The people who were in the diet study ... we had them consume the exact same meals, at baseline and then again after receiving genetic information. And what we found was that when people were told that they were genetically predisposed to feel less full, they felt less full than people who were told they were genetically predisposed to feel more full.

"We were particularly interested in not just the subjective response, how you felt in response to this genetic information, but the body's physiological response. What we found in this study is that it changed their body's response. So in the diet study, we found that those who were told they were protected, who were going to feel more full, actually physiologically had more of this fullness hormone than those who were told they're at risk.

"What we think is going on, and we've seen in a number of different studies in which our mind influences the body, is that there are these direct effects — your mind is trying to predict what's going to happen, and the brain, being intricately connected to ... every system in the body, changes things. It adapts in order to prepare for what it thinks is going to occur next. So when the brain thinks, 'I'm not eating enough, I'm going to feel full,' it changes its physiology accordingly."

On physiological impacts observed in the exercise experiment

Turnwald: "In the running experiment, we had participants hooked up to a mask in which we measured their oxygen and carbon dioxide output in every single breath throughout the course of their running tests, and what we found was that people who we told had increased genetic risk, it decreased their lung capacity by about two liters of air per minute. So that's just the sheer amount of air that they're moving into and out of their lungs per minute. And it also decreased their ability to remove toxic carbon dioxide buildup."

On the takeaways from this research with regard to genetic testing and information

Crum: "The answer isn't really so simple. The answer is not, 'Hey, don't get genetic testing, it's going to make you worse.' It's, 'Hey, be mindful that receiving genetic risk puts you in a mindset,' and that mindset can have an impact on your body as well as how you feel and how you behave.

"We're not saying that you shouldn't receive genetic information. What we're learning about genes is really important, but our genetic makeup is just one piece of the puzzle. Our mindsets are another piece — an often-overlooked piece — and this work that Brad and our team at Stanford has done is just the tip of the iceberg in understanding the role of mindsets in genetic information."

Karyn Miller-Medzon produced and edited this interview for broadcast. Jack Mitchell adapted it for the web.


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