Genetic testing is becoming increasingly popular. Some estimate that one in 25 American adults have gotten personalized genetic tests both indoctors'offices and in direct-to-consumer tests (e.g., 23andMe). There can be profound benefits to this kind of testing: genetic risk estimates are now available for 10,000 conditions and16,000 genes, including for things like Alzheimer's, breast cancer, and obesity.

A recent study investigated the impacts of receiving genetic tests for obesity. We will analyze one of their results: the impact on physiological exercise capacity, as measured by CO2: O2exchange rate. Physiological exercise capacity is in contrast to subjective exercisecapacity like "this is challenging" or "I feel tired." Their study design included the following sequence: Participants were genotyped for actual genetic risk (and not told of their results). Then participants were asked to run on a treadmill to assess baseline exercise capacity. The scientists measured five measures of exercise capacity, here we will only analyze physiological capacity, CO2 : O2 exchange rate. Then participants were randomly assigned to groups and told either that their genotype confirmed they are "high-risk" for obesity or that their genotype confirmed they are "protected" from obesity.

This random assignment was regardless of their actual genotype, which means that half of the participants had an assignment that matched their genotype and half had an assignment that did not match their genotype. Then participants were asked to participate in the identical running task (on a treadmill) and the same outcome was measured (e.g., CO2 : O2 exchange rate). This figure shows a schematic of the experimental design. In each participant, scientists compared the CO2 : O2 exchange rate before and after the participant was told their genotype. Their results are shown in Figure 1. Participants who were told they have a genotype that is protective had a greater increase in CO2 : O2 exchange rate compared to participants who were told they were high risk. In other words, participants who were told they had a protective genotype had a greater physiological exercise capacity -regardless of their actual genotype.

QUESTIONS AND USE THIS LINK https://www.nature.com/articles/s41562-018-0483-4?_ke=eyJrbF9lbWFpbCI6ICJraXRhc2hlZXRzQGdtYWlsLmNvbSIsICJrbF9jb21wYW55X2lkIjogIm15NzV5NiJ9

1. This study shows an example of a placebo effect impacting physiological exercise capacity. If scientists had measured subjective exercise capacity (e.g., time until the participant felt tired, or how challenging the running seemed), do you think the placebo effect would be the same, more extreme, or less extreme? Comment on your perception of the placebo effect on physiological exercise capacity vs. the placebo effect on perceived exercise capacity. Do those two seem different to you? Is there one that you "believe" more?

2. The authors of the paper state "In spite of its benefits, this [experimental] design is ethically challenging. Randomly assigning participants to learn that they have a high or low genetic risk necessitates deception, as some participants must be falsely informed of their genotype in an ethical, yet believable, manner." Nonetheless, they justified their design by using risk of obesity as the genetic marker, not risk of cancer or other immediately terminal illness, and by limiting the time in which the participants were deceived (1 hour only). What is your opinion about the ethics of this design? Things you might consider include: Are there other factors that you would want to ensure to prevent harm to the participants? Is the finding they presented in the paper "worth the potential harm" to the participants? Etc.

3. The paper that presented these results says, "Merely receiving genetic risk information changed individuals'cardiorespiratory physiology...If simply conveying genetic risk information can alter actual risk, clinicians and ethicists should wrestle with appropriate thresholds for when revealing genetic risk is warranted." Said another way, if deceiving participants can elicit positive physiological responses, are there situations in which this deceit is warranted? This is a question that is likely to elicit very strong opinions and opinions that differ dramatically between people. That is ok. Using kindness, your moral compass, and your logic, please tell me what you think.