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The placebo effect: belief and biology – part II

by Jonathan Robison, PhD, MS

In Part I we discussed a study in which room attendants from 7 different hotels were randomly assigned to one of two experimental conditions. Subjects in both conditions received written materials describing the benefits of exercise. They were also given specific information about how many calories they were expending in the various activities of their daily work. In the informed condition only, the subjects were also shown how that amount of activity more than met current recommendations for a healthy lifestyle. 

Systolic and diastolic blood pressure, BMI, body weight and waist-to-hip-ratio all decreased in the informed group only, even though subjects self-reported diet, activity (off the job) and substance use (caffeine, alcohol, cigarettes) indicated no changes over the 4-week period. In the informed group, the percentage of subjects who reported exercising regularly doubled, even though the physical activity involved with their work did not change. The authors concluded that the observed physiological changes were likely a result of the subjects increased perceived exercise.

We asked, can placebos actually have this kind of impact on our physiology? If so, do we have any idea how this might happen? We discussed that there are decades of good quality research demonstrating the power of placebos to impact our physiology. In fact, the placebo effect is so powerful, that it appears to operate even when people know they are taking a placebo. Though the mechanisms have not been completely elucidated, we are beginning to understand the most likely explanations. According to a recent article in the prestigious British medical journal, The Lancet:

The overall outcome of a treatment combines the specific pharmacological or physiological aspect of the treatment and the psychosocial context in which it is delivered. The psychosocial context represents the placebo component which is based on patient expectations.

It appears that patients’ expectations about their treatment can stimulate the release of chemicals in the body that result in the physiological changes we see with placebos. Endogenous opiods like endorphins and neuropeptides like dopamine and serotonin have been implicated in this connection between belief and biology. What is fascinating is that these chemicals are often the same ones that are released by the real drugs themselves. Again, quoting from the Lancet:

 Placebo mechanisms can interact with drug treatments even if no drug is given, since every treatment is given in a therapeutic context that has the potential to activate and modulate placebo mechanisms, many of which can act on similar biochemical pathways to the actual drug.

 The practical implications of this knowledge are profound. No matter what the therapeutic encounter, the healing/curing process involves not only any biomedical intervention that might occur, but also how patients feel about that intervention, which is based on their attitudes and beliefs and on the quality of the relationship with their health care professional. There is perhaps no better proof of the mind and body connection than the placebo effect. Everything that happens in the therapeutic encounter matters!

Could the placebo effect explain the physiological changes that occurred in the informed group? Or, is it true as one medical expert commented, that people’s perceptions can only affect “subjective types of findings” like a person’s perception of pain or their sense about whether they feel depressed. Is it possible that the perception of increased exercise reduced the stress of worrying about not getting enough exercise to the point of reducing blood pressure? Given what we have seen about the power of placebos, this seems to be at least a possibility. Remember the study from Part I in which the implanted (but not activated) pacemakers modulated aberrant heart rhythms in people with neurocardiogenic syncope?

But, what about the researchers’ contention that BMI, weight, body fat percentage and waist to hip ratio all changed as a result of people’s “mindset” about exercise? In spite of the documented power of placebos, we have a way to go before we can make this connection. The more likely probability is that behaviors in the informed group were altered as a result of their attitudes and beliefs. As the researchers’ themselves confess:

It is possible that the room attendants actually did change their behavior – actually did cut back on calories improve the quality of the food they ate, or work harder or more energetically – but did not report such changes.

 Interestingly, they go on to say that this is an unlikely explanation because “previous research has found it very difficult to change behaviors of this sort.” In terms of weight loss, this seems a dubious contention given that many people initially lose weight on all sorts of interventions. The approximately 2 pound loss in the informed group is compatible with short term changes in physical activity and/or diet.

It is certainly possible that the therapeutic encounter contributed to changes in behavior that led to changes in weight-related parameters.  If sustained, these behavioral changes could contribute to improved health in these individuals. The focus of the article however (and even more so of the media coverage of the research) was on the weight changes as being “healthy” and desirable in and of themselves. As one writer put it – “maybe it really might be possible to sit on the couch eating chocolates and lose weight.”  The fallacy here (oh so surprisingly) is in equating changes in weight with changes in health. In fact, the average BMI of the people in the informed group was in a range (around 26) where people actually live the longest and the change of 2 pounds keeps them in that same range. The changes in waist to hip ratio and body fat percentage were too small to have much practical significance – if they have any significance at all.

So, what is the bottom line? The intervention may have changed people’s perceptions about exercise and their health. This may have impacted their blood pressure and perhaps changed some physical activity and diet-related behaviors. The weight-related changes were most likely the result of the altered behaviors, not good or bad or healthy or unhealthy in and of themselves — right in line with the philosophical approach to weight and health that we all are working so hard to promote.

 ps – A number of people requested more information on the Nocebo effect – I will be happy to address that in my next blog – take care – Jon

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