The Amazing Power of the Placebo EffectPlacebo effects have been shown in many different areas in science.  Sometimes placebo effects have been shown to mimic or even exceed effects produced by active treatments (such as therapies or medications).

The definition of placebo is an inert, inactive, fake, sham, dummy, non-therapeutic, pseudo, or spurious substance or procedure presented as a treatment for any of a number of conditions.

In general, the placebo effect can be defined as a positive effect that occurs after receiving treatment (interaction, therapy, medication), even when the treatment is inert (inactive, fake).

The placebo effect is a ubiquitous phenomenon.  We all experience some degree of the placebo effect on a regular basis.

The power of the placebo effect is illustrated in the movie classic, The Wizard Of Oz.  The wizard didn’t actually give the scarecrow a brain, the tin man a heart, and the lion courage, but they all felt better anyway (Stanovich, 2007).

It can be expected that the benefits obtained from any treatment are at least partially due to placebo effects.  “[S]ubjects typically know they are getting some kind of treatment, and so we may rarely be able to measure the actual effects of a drug by itself.  Instead, we see the effects of treatment plus placebo effects that are shaped by the subjects’ expectations.  We then compare those effects with the effects of placebo alone” (Myers and Hansen, 2002).

A common statement heard when discussing placebo effects goes something like this; it’s not real it’s the placebo effect, it’s just in your head.  This is an erroneous viewpoint.  Placebo effects often produce robust neurobiological and other physiological effects that are very real.  This fallacious assumption can be at least partly attributed to the belief that the mind and body are somehow separate.

In this video segment on YouTube, Paul Bloom, a cognitive scientist and author, talks about the mind versus the brain.  He maintains that although the mind and the brain are “one and the same,” most people intuitively “at a gut level think the mind is separate from the brain.”

According to Bloom, “The mind is a product of the brain.  The mind is what the brain does.”  Considering them separate entities may be derived from belief in dualism–that the soul is an immaterial entity separate from the body (another subject for another day).  Bloom briefly mentions substance dualism in the link provided above.

Possible mechanisms contributing to the placebo effect include:

  • Suggestions and expectations
  • Classical conditioning
  • Anxiety reduction hypothesis

Other mechanisms are sometimes mentioned when explaining the constituents of the placebo effect, but the three mentioned above are probably the mostly widely discussed.  Of course, in many conditions they overlap and their interaction shapes the placebo effect.

The quotes below are excerpts taken from The placebo-nocebo effect: how symbols can heal and kill, an article by Fabrizio Benedetti, a professor of clinical and applied physiology at the University of Turin Medical School:

The placebo-nocebo effect represents an amazing example of how the mind-brain unit interacts with the body. Whereas placebos have to do with positive symbols that anticipate clinical benefit, nocebos are linked to negative symbols that induce expectations of clinical worsening. Positive symbols can range from empathic doctors and smiling nurses to trust-inducing complex medical machines and apparatuses.

By studying placebo and nocebo effects, today we are beginning to understand how medical symbols affect the patient’s brain or, in other words, how positive or negative psychosocial contexts can change the brain and body functioning of the patients.

Continue reading Part 2 of this series about the placebo effect.


Myers, A., & Hansen, C. (2002).  Experimental psychology.  Pacific Grove, CA: Wadsworth.

Stanovich, K. (2007).  How to think straight about psychology.  Boston, MA: Pearson.



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From Psych Central's World of Psychology:
Nocebo Effect, the Other Side of Placebo - Psych Central | World of Psychology (8/21/2011)

    Last reviewed: By John M. Grohol, Psy.D. on 21 Aug 2011
    Published on All rights reserved.

APA Reference
Hale, J. (2011). The Amazing Power of the Placebo Effect. Psych Central. Retrieved on March 23, 2015, from


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