Does a medical diagnosis become a self- fulfilling prophecy? The power of words as a nocebo or placebo.

Genetic tests have become a consumer product. It is thought that over 21% of Americans have now bought a genetic test. You can buy reports that assess your risk for over 10,000 conditions. These include Alzheimer’s, all kinds of cancer and obesity. What is the impact of receiving such a report? Does it affect you psychologically and behaviourally? Do you worry and start taking vitamins? Does it actually affect you physiologically?

The Mind and Body are not Separate.

Researchers at Stanford University set out to explore whether a genetic test result would impact the body. They focused on two different genes. One related to exercise and the other obesity. The framework for the two studies was identical. Respondents took a base case medical test. They then had a genetic test. There is a gene known to influence exercise. Individuals with the gene are less effective when exercising. Exercise has less impact on their body. They tend to get hotter when working out. There is a gene associated with obesity. The gene affects the ability to be satiated, to feel full.

The individuals in the two studies were then fed back the results of their tests. Except that the findings were randomly assigned. Half the people with the gene were told that they had it and half that they did not. Half the people without the gene were told that they had it and half not. A week later participants were retested. Immediately afterwards the full nature of the study and the actual results were shared. Each participants received individual feedback. This was to ensure no harm was done by the false diagnoses.

Being given the diagnosis affected the body. The study of exercise provides a good example. In the base tests people ran on a treadmill until exhausted. Their respiratory power was assessed. The capacity to supply muscles with energy and the volume of air inhaled and exhaled were measured throughout their run. They took the gene test and later were told the “result”. A week later they returned to the treadmill and repeated the test. During the second test they were asked to report how hot they felt.

Simply informing participants that they had the gene changed the results. Exercise capacity changed. It lowered the maximum capacity to supply oxygen to the muscles. The amount of air supplied to the lungs was reduced by 2 liters per minute. When told to run until exhausted they ran for less time, compared to their results before diagnosis. There was a marked slowdown in the last few minutes of the run. The most difficult part of the test. They also reported feeling hotter. All of this happened based on the diagnosis independent of whether it was true.

The obesity test measured a peptide. It is released by the stomach to indicate to the body that is satiated or full. The diagnosis produced a 2.5 fold increase in physiological satiety. There was a 1.4 fold increase in self-reported fullness. This was compared to eating the same meal at the same time one week earlier.

The researchers tested the relative impact of the “perceived diagnosis” versus the real diagnosis. The "perceived diagnosis" had a separate effect. It had as big an impact as the real diagnosis in many of the tests.

The Power of Words

The study raises all kinds of issues particularly for the ageing. There is obviously an issue with the model of consumer gene testing. The reports contain gene risk profiles for diseases with a far bigger impact than exercise and obesity. There is no counselling provided or follow-up. For some a diagnosis means a loss of control and a sense of inevitability. In other Newsletters I have discussed the relative impact of the genome and exposome. Our genes determine less than 20% of our health. Some diseases are more dependent on our genes, others much less so. Gene diagnoses are probabilities not absolutes.

At a more general level any diagnosis can potentially have a negative effect. This is particularly the case with chronic diseases of age. We know these diseases cannot be cured only treated. To be told one has diabetes carries with it the “Google” description. We look up the symptoms. We look up the progression. Does it become self-fulfilling?

This study is very specific and measures a short-term impact. It is an indication, no more. Longer studies would probably not pass the ethics committees that approve such experiments. Leaving someone with a false diagnosis for a longer period of time would be unacceptable. Using cancers or Parkinsons Disease as the relevant gene similarly would be seen as to big a risk to the participants.

The Doctors’ Dilemna

As Ellen Langer points out the problem is that all diagnoses are probabilities . We have all read our blood test results. With ranges defining thresholds for what is normal. When are we normal, pre-diabetic, and when diabetic? The results themselves have a margin of error. The tests are not perfect and can be influence by many outside factors. Those thresholds are judgements based on available data. Our doctor makes another judgement based on them. Diagnosis appears to be cost free. It opens up a path to treatment. To make a diagnosis is the key role of a doctor. What studies like this show is that making a diagnosis is not cost free.