Theories Surrounding the Cause of the Placebo Effect
There are several theories as to why the placebo effect occurs and who is more likely to respond to a placebo treatment. These theories are discussed below.
Natural Remission Theory
This theory embraces the concept that any benefit the patient experiences from a placebo is based solely on a natural improvement in the ailment or coincidence. This implies that the placebo effect is not due to the placebo itself but some natural course of the disease. For example, a headache, which is not considered a long-lived ailment, would likely subside naturally.
Expectancy and Personality
Expecting that a treatment will work or will fail has been considered one of the most influential predictors of the placebo effect and may be found at the heart of the placebo effect. Expectancy tends to go hand in hand with personality, specifically, optimists and pessimists. Some studies have shown that in a group of optimistic and pessimistic participants, when given a placebo and told that it will improve their condition, optimists tend to respond better to the placebo than pessimists.
Regression to the Mean
This theory is similar to that of the Natural Remission Theory and states that if the initial outcome of using a placebo is intense (positive or negative) it is likely that if the placebo was given again the outcome would be statistically closer the average of the collected data or the mean. An article by Sundararajan Rajagopal provides the example of a trial in patients with critical disease. In this case patients with a condition such as severe depression and suffering from intense symptoms at the beginning of a clinical trial, when they are assessed later in the trial it is likely that the patients will show an improvement in symptoms.
Conditioning
This theory relates to the idea that a patient has had a positive response to medications or a specific treatment in the past. Because the patient has had such a positive or influential experience, when the patient receives a medication or treatment in the future, they will expect to benefit from this. The diagram below demonstrates conditioning utilizing the theory of "Pavlov's Dog". For more information on Pavlov's famous experiment please see the additional resources page of this website.
There are several theories as to why the placebo effect occurs and who is more likely to respond to a placebo treatment. These theories are discussed below.
Natural Remission Theory
This theory embraces the concept that any benefit the patient experiences from a placebo is based solely on a natural improvement in the ailment or coincidence. This implies that the placebo effect is not due to the placebo itself but some natural course of the disease. For example, a headache, which is not considered a long-lived ailment, would likely subside naturally.
Expectancy and Personality
Expecting that a treatment will work or will fail has been considered one of the most influential predictors of the placebo effect and may be found at the heart of the placebo effect. Expectancy tends to go hand in hand with personality, specifically, optimists and pessimists. Some studies have shown that in a group of optimistic and pessimistic participants, when given a placebo and told that it will improve their condition, optimists tend to respond better to the placebo than pessimists.
Regression to the Mean
This theory is similar to that of the Natural Remission Theory and states that if the initial outcome of using a placebo is intense (positive or negative) it is likely that if the placebo was given again the outcome would be statistically closer the average of the collected data or the mean. An article by Sundararajan Rajagopal provides the example of a trial in patients with critical disease. In this case patients with a condition such as severe depression and suffering from intense symptoms at the beginning of a clinical trial, when they are assessed later in the trial it is likely that the patients will show an improvement in symptoms.
Conditioning
This theory relates to the idea that a patient has had a positive response to medications or a specific treatment in the past. Because the patient has had such a positive or influential experience, when the patient receives a medication or treatment in the future, they will expect to benefit from this. The diagram below demonstrates conditioning utilizing the theory of "Pavlov's Dog". For more information on Pavlov's famous experiment please see the additional resources page of this website.
Remembered Wellness
In this theory, (similar to that of conditioning above), the patient takes a placebo and remembers a time when he or she felt better. It is not necessarily linked to taking a previous medication that worked for the patient but it has shown the remembering a time of wellness alters brain chemistry.
References:
1. Rajagopal S. The placebo effect. Psychiatric Bulletin. 2006;30:185-188.
2. Jaksic N, Aukst-Margetic B, Jakovjeciv M. Does personality play a relevant role in the placebo effect? Psychiatr Danub. 2013;25(1):17-23.
3. Placebo Effect. American Cancer Society. http://www.cancer.org/treatment/treatmentsandsideeffects/treatmenttypes/placebo-effect. Updated October 4, 2012. Accessed May 28, 2013.
Images courtesy of:http://crowncddt.com/technology/
http://chubbedupelvis.blogspot.ca/2012/05/feeling-sick.html
http://littlemisspinaycrafter.blogspot.ca/2012/02/one-about-cupcake-stand.html
http://www.irishhealth.com/article.html?id=17318
http://commons.wikimedia.org/wiki/File:Equals_sign_in_mathematics.jpg
http://s572.photobucket.com/user/Treadtrader/media/thumbs-up-happy-face.jpg.html
1. Rajagopal S. The placebo effect. Psychiatric Bulletin. 2006;30:185-188.
2. Jaksic N, Aukst-Margetic B, Jakovjeciv M. Does personality play a relevant role in the placebo effect? Psychiatr Danub. 2013;25(1):17-23.
3. Placebo Effect. American Cancer Society. http://www.cancer.org/treatment/treatmentsandsideeffects/treatmenttypes/placebo-effect. Updated October 4, 2012. Accessed May 28, 2013.
Images courtesy of:http://crowncddt.com/technology/
http://chubbedupelvis.blogspot.ca/2012/05/feeling-sick.html
http://littlemisspinaycrafter.blogspot.ca/2012/02/one-about-cupcake-stand.html
http://www.irishhealth.com/article.html?id=17318
http://commons.wikimedia.org/wiki/File:Equals_sign_in_mathematics.jpg
http://s572.photobucket.com/user/Treadtrader/media/thumbs-up-happy-face.jpg.html