Placebo Effect Experiments, Studies, and Causes

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The placebo effect is the phenomenon in which some people experience a benefit after the administration of an inactive substance or sham treatment.

A placebo is a substance with no known medical effects, such as sterile water, saline solution, or a sugar pill. A placebo is a fake treatment that in some cases can produce a very real response. The expectations of the patient play a significant role in the placebo effect; the more a person expects the treatment to work, the more likely they are to exhibit a placebo response.

Use of Placebos in Medical Research

In medical research, some patients in a study may be administered a placebo while other participants receive the actual treatment. The purpose of doing this is to determine whether or not the treatment has a real effect. If participants taking the actual drug demonstrate a significant improvement over those taking the placebo, the study can help support the claim for the drug's effectiveness.

Examples of the Placebo Effect

For example, let's imagine that a participant has volunteered for a study to determine the effectiveness of a new headache drug. After taking the drug, she finds that her headache quickly dissipates, and she feels much better. However, she later learns that she was in the placebo group and that the drug she was given was just a sugar pill.

One of the most studied and strongest placebo effects is in the reduction of pain. According to some estimates, approximately 30 to 60 percent of people will feel that their pain has diminished after taking a placebo pill.

The Placebo Effect in Psychology Experiments

In a psychology experiment, a placebo is an inert treatment or substance that has no known effects. Researchers might utilize a placebo control group, which is a group of participants who are exposed to the placebo or fake independent variable. The impact of this placebo treatment is then compared to the results of the real independent variable of interest in the experimental group.

Even though placebos contain no real treatment, researchers have found they can have a variety of both physical and psychological effects. Participants in placebo groups have displayed changes in heart rate, blood pressure, anxiety levels, pain perception, fatigue, and even brain activity. These effects point to the brain's role in health and well-being.

What Causes the Placebo Effect?

Research is ongoing as to why some people experience changes even when they are only receiving a placebo. One possible explanation is that taking the placebo triggered a release of endorphins. Endorphins have a structure similar to morphine and other opiate painkillers and act as the brain's own natural painkillers.

Researchers have been able to demonstrate the placebo effect in action using brain scans, showing that areas that contain many opiate receptors were activated in both the placebo and treatment groups. Naloxone is an opioid antagonist that blocks both natural endorphins and opioid drugs. Using naloxone, placebo pain relief is reduced.

Other possible explanations include conditioning, motivation, and expectation. In some cases, a placebo can be paired with an actual treatment until it comes to evoke the desired effect, an example of classical conditioning.

People who are highly motivated to believe that a treatment will work, or who had a treatment work previously, may be more likely to experience a placebo effect.

Conversely, individuals can experience negative symptoms as a response to a placebo, a response that is sometimes referred to as the "nocebo effect." For example, a patient might report having headaches, nausea or dizziness in response to a placebo.

Sources:

Eippert F, Bingel U, Schoell ED, et al. Activation of the Opioidergic Descending Pain Control System Underlies Placebo Analgesia. Neuron. 2009;63(4):533-543. doi:10.1016/j.neuron.2009.07.014.

Hróbjartsson ACB, Gøtzsche PC. Placebo interventions for all clinical conditions. Cochrane Database of Systematic Reviews. 2010. doi:10.1002/14651858.cd003974.pub3.

Placebo Effect. American Cancer Society. https://www.cancer.org/treatment/treatments-and-side-effects/clinical-trials/placebo-effect.htm.

Plotnick R, Kouyoumdjian H. Introduction to Psychology. Cengage Learning. 2013

Weiner IB, Craighead WE. The Corsini Encyclopedia of Psychology, Volume 3. Hoboken, NJ: John Wiley & Sons. 2010.

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