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Dudley Dowell
Tue, May 05, 2015 - 12:00 AM

What is the placebo effect and how does it work?

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Bo Bennett, PhD
Host, Doctor of Social Psychology


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Bo Bennett, PhD

Host, Doctor of Social Psychology


About Bo Bennett, PhD

I am the host of this show :) For my complete bio, please see
PrintTue, May 05, 2015 - 12:00 AM
The word "placebo," Latin for "I shall please," is generally understood in modern terminology as an inert (inactive) substance or procedure that affects the outcome of a treatment. The placebo effect (or placebo effects) is generally understood as the improvement in a person's condition due to the presence of the placebo. However, this concept is far more complex than most people realize, but it is within this complexity we find understanding. There has been an enormous amount of research over the past 50 years on placebos, and while the exact mechanisms are not fully understood, we do know enough to separate the facts from myths and the science from the "woo."

The Controversy

The study of placebos tends to be a controversial topic in academia. The controversy surrounding placebos can be summed up as follows:

1) Is there really such thing as a placebo effect? And if so, how can we define it?
2) What does this mean for the "mind-body connection"?
3) If placebo-based deception has a significant effect on the patient's health, does that justify its use?

Addressing all three of these concerns will simultaneously provide a more complete answer to the main question, "what is the placebo effect and how does it work?"

Is there really such thing as a placebo effect?

We can answer this question either yes or no, since the answer is dependent upon semantics. For example, if we define a placebo as "an inert substance or procedure," by definition it cannot have an effect since that is what "inert" means, so the term "placebo effect" is self-contradictory. If your doctor prescribes you a completely inactive substance such as a sugar pill, because she knows it will make you feel better, it's clearly not the pill that will make you feel better, but something else. This "something else" is what researchers refer to as the psychosocial context of the therapeutic intervention (Benedetti, 2005). Research has clearly shown that an empathetic doctor has an effect on how one feels after a visit to the doctor (Walach & Jonas, 2004). But this doctor/patient interaction has nothing do with the sugar pill itself. In fact, there are many factors that have been empirically shown to affect the outcome of a therapeutic intervention that are better explained as meaning responses, or physiologic or psychological effects of meaning in the origins or treatment of illness' (Moerman & Jonas, 2002). So if we move these demonstrable effects from "placebo effects" to "meaning responses," one can argue that it is an issue of semantics and we are still talking about essentially the same thing: the interpretation of a situation that has measurable psychological, physiological, and/or biological effects on the person doing the interpreting.

Walach and Jonas (2004) combed through decades of research and collected 18 ways in which the magnitude of the placebo effect (or meaning response) can be affected by health care professionals. Some of these include using more frequent dosing rather than less frequent dosing—up to a limit, applying therapies in therapeutic settings such as hospitals and clinics, delivering therapies in a warm and caring way, delivering therapies with confidence and in a credible way, using the newest and most prominent treatment available, using a well known name brand identified with success (i.e., marketing can make a drug more effective), and touching the patient.

Kienle and Kiene (1997) wrote a critique of Henry K. Beecher's original article on "The Powerful Placebo" in which Beecher's 1955 study claimed that out of 15 trials evaluated, 35% of the 1082 participants were relieved by placebos alone. Kienle and Kiene concluded that other factors not related to even a broad definition of the placebo effect accounted for Beecher's results, including spontaneous improvement, regression to the mean, fluctuation of symptoms, additional treatments, and answers of politeness, just to name a few. The authors further claim that in a review of over 800 articles on placebos, they found "no reliable demonstration of the existence of placebo effects." Regardless of whether the authors may have extended their skepticism too far to the point of unscientific cynicism, they have identified many other effects and factors that are often subsumed under the placebo effect, yet are something very different. It is through sloppy methodology that researchers often fail to separate these factors from what they call "placebo effects." Kirsch (2013) points out that researchers often use the terms "placebo response" and "placebo effect" synonymously, when the two are different. This fact supports Kienle and Kiene's argument since a response is and observed change and an effect is a change produced by the intervention. Correlation does not equal causality, and as Kienle and Kiene would argue, a spontaneous improvement cannot be automatically credited to the placebo.

The best way to conduct research that isolates placebo effects includes having three groups: one group that receives the treatment being tested (e.g., the group that gets the medicine with the active ingredients), one group that gets the placebo (e.g., the group that gets the sugar pill but thinks it is the medicine with the active ingredients), and one group that gets nothing. This last group (the control group) should be minimally interacted with because even the slightest interaction could be interpreted as part of a meaning response (e.g., where the researcher sympathetically listens to the participant talk about her illness) and affect the outcome of the individuals in the group.

Kienle and Kiene's rejection of placebo effects can be a matter of semantics, since they do acknowledge that psychosomatic effects "undoubtedly" exist, which are loosely defined as effects "relating to the interaction of mind and body." This brings us to the second point of controversy.

What does this mean for the "mind/body connection"?

In the field of science, it is ubiquitously understood that the mind is a result of the physical brain, and mind/body dualism is a relic of theology and the pre-scientific age. In this light, the mind/body connection is less mysterious. We know that the brain (specifically the hypothalamus) influences the bodily functions through the autonomic nervous system (ANS), even though the vast majority of these functions (such as breathing, heart rate, digestion, etc.) occur at the unconscious level. The real question is what processes can we have conscious control over and to what degree? This is where we see answers provided by science, pseudoscience, and science fiction. For example, therapeutic hypnosis can be very effective for reducing pain. In fact, there is little controversy over the many subjective experiences and bodily functions over which we have greater control (i.e., respiratory rate, sexual arousal, etc.) and it is no surprise that these are where we find the majority of placebo effects. However, there have also been some surprising findings where researchers have found placebo effects in improved muscle performance in Parkinson's patients (Price, Finniss, & Benedetti, 2008). Our understanding, or lack of understanding, of the mind/body connection has been a breeding ground for alternative medicine supporters, self-help gurus, and practitioners of woo to make claims far beyond the scope of what has been demonstrated in science, such as the idea that positive thinking can cure cancer. Then we have the science-fiction where in the film "Lucy" (Lucy played by Scarlett Johanson) uses 100% of her brain (based on the 10% of brain use myth) to access superhuman strength and healing powers. We would be wise to remember an important concept in critical thinking here: possibility is not the same as probability, and outrageous and unsupported claims cannot be made simply because they are not impossible.

The mind is often described as a "black box" within psychology—especially within behaviorism, meaning that we can feed in inputs, and sometimes predict the outputs with great accuracy, but we are still not sure what exactly is going on inside the box. Researchers can point to concepts such as expectancy, memory or past treatments, desire, goals, somatic focus, suggestion, classical conditioning, and cues that signal that an active med or treatment has been given (Price, Finniss, & Benedetti, 2008) as a mechanism for the placebo effect, but in many cases, we are still dealing with the black box. There are some hypotheses that do provide a more complete connection between the function of the mind and the biological connection. For example, one hypothesis states that executive attention (distraction) can reduce anxiety which in turn reduces pain (Benedetti, 2005) or when it comes to the immune system, being able to appraise one's situation in a less stressful way decreases secretion of hormones such as cortisol, which would otherwise lower resistance to disease.

If placebo-based deception has a significant effect on the patient's health, does that justify its use?

Let's put health-related issues into two general categories: those that can be cured by a therapeutic intervention (i.e, medicine, surgery, etc.) and those where only the symptoms can be alleviated (i.e., common cold, terminal cancer, etc.). In the latter category, does it really matter if you go to a traditional doctor and his interaction with you makes you feel better, or you go to a witch doctor, and the interaction still makes you feel better? Perhaps not. But the problems arise when one forgoes science- and evidence-based care for an alternative treatments that are no better than placebo when the underlying problem isn't being addressed and it could be. One could also argue that selling a treatment with results no better than placebo allows people to take advantage of others by preying on their desperation. But a treatment that has not been found to be any better than placebo can still be very effective when it comes to subjective feeling such as pain relief (not elimination of the disease). Another problem is that patients ascribe healing powers to pills and procedures that have no intrinsic therapeutic value for the condition being treated, which is simply counter factual and contributes to poor critical thinking. As far as the ethics are concerned for a licensed doctor knowingly administering a placebo for the symptoms, even when there is no known treatment for the underlying issue, this remains a hotly debated area of discussion.

It might be tempting to think that disorders, diseases, and illnesses that are found to be affected by placebo effects are "all in the head" and people can simply change their thoughts to cure themselves, but this is not the case. Just because there is a mind/body connection, does not mean we have conscious mastery over it. A physiological phenomenon such as pain is a subjective experience, so by definition, "all in the head," but these experiences are almost always a result of a biological condition (e.g., a cut finger). As we begin to understand more about this connection, placebo effects, and meaning responses, we are finding ways to better manage these disorders, diseases, and illnesses through conscious processes. But we should be careful not to read too much into placebo effects, confuse placebo effects with sloppy methodology, or ignore the seriousness of real health issues simply because the symptoms of such issues can be made better by placebo effects. If there is a single conclusion we can draw it is that the mind is an amazing thing and we still have a lot to learn about it.

Benedetti, F. (2005). Neurobiological Mechanisms of the Placebo Effect. Journal of Neuroscience, 25(45), 10390–10402.
Kienle, G. S., & Kiene, H. (1997). The powerful placebo effect: fact or fiction? Journal of Clinical Epidemiology, 50(12), 1311–1318.
Kirsch, I. (2013). The placebo effect revisited: Lessons learned to date. Complementary Therapies in Medicine, 21(2), 102–104.
Moerman, D. E., & Jonas, W. B. (2002). Deconstructing the placebo effect and finding the meaning response. Annals of Internal Medicine, 136(6), 471–476.
Price, D. D., Finniss, D. G., & Benedetti, F. (2008). A Comprehensive Review of the Placebo Effect: Recent Advances and Current Thought. Annual Review of Psychology, 59(1), 565–590.
Walach, H., & Jonas, W. B. (2004). Placebo research: the evidence base for harnessing self-healing capacities. Journal of Alternative & Complementary Medicine, 10(Supplement 1), S–103.

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Linda Williams
Wednesday, May 06, 2015 - 11:04:13 AM
Back in the mid 60's, my mother in law was a chronic complainer, going to the Dr all the time with one ailment after another. When I realized she had accumulated a medicine cabinet full of Proscribed bottles of pills, ( having believed all these ailments were in her head), I visited her Dr to demand what was wrong with her. After our talking around the issue, and talking Hypothetically, he finally told me that all those bottles of pills were nothing but sugar pills and he realized there was really nothing wrong with her, but if her thinking the pills are making her feel better, what was the harm? Thanks for the interesting post!

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Chad Whitney, RN
Wednesday, May 06, 2015 - 03:24:20 AM
Then there is me, lol! As a registered nurse, I often assess and treat pain in severely obtunded and comatose patients. These patients obviously cannot verbally convey their needs. Conscious control is out of the picture completely. This is especially true when working in the trauma/neuro intensive care unit. I rely heavily on autonomic responses. Sympathetic activation will tell me when a person is in pain, or experiencing discomfort. Parasympathetic activation guides me in assessing the effectiveness of my intervention. In my case, that intervention might range from administration of a simple intravenous narcotic or benzodiazepine push, on up to a continuously running IV paralytic/opiate combination (when being mechanically ventilated, of course.) It is not all bad… there is a beneficial flipside to taking care of people who cannot speak ;)

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