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The Power of Positive Thinking: The Placebo Effect

Mimi N.'s picture

Wouldn’t it be great if eating some sugar could alleviate pain, cure a cold, or even cancer? Recent studies suggest this may be possible due to a placebo effect.

In Latin the word “placebo” means “I will please.” In the medical field a placebo is known as a pharmacologically inert substance which may produce therapeutic results because of the belief in its efficacy (1). In research, a placebo is an inactive substance or procedure, which on its own has no effect, used as a control. A placebo effect takes place when the subject given the placebo demonstrates similar results as the experimental substance or procedure (3).


People have been trying to distinguish the relationship between body and mind for thousands of years. Plato’s Theory of Forms suggests that the material objects around us are just abstractions of the real world, and that for our intellect to interact with such entities, it must be inherently non-physical. Thomas Aquinas, a Christian philosopher, said that while the soul can exist independently of the flesh, it must be a part of the human body to become a true person. Rene Descartes, a French philosopher, is the most well known for his theories on mind and matter. The Cartesian Dualism claimed that immaterial mind and the material body are two completely separate entities that somehow manage to interact and exert control over each other. Later in the early 19th century, German physician Johann Christian August Heinroth coined the term “psychosomatic,” referring to his theory that the mind can encourage both mental and physical illness. Later in the 19th century Hippolyte Bernheim, a French internist and hypnotism-advocate, developed the Suggestion and Autosuggestion theory, describing the psyche’s influence over illness, and what is known today as the placebo effect (1).


Researchers have been studying the placebo effect for decades. The first major groundbreaking study was done by H.K. Beecher in 1955, in which he reported in his paper “The Powerful Placebo” that across 26 studies an average of 32% of the patients responded to a placebo (2). Many theories have been proposed to explain this phenomenon. Benefit from attention, stimulus response, beliefs or expectations, relationship with the doctor, and a desire to please the doctor are a few (7). One of the most prominent theories is similar to Pavlov’s classical conditioning theory. In the same way which Pavlov’s dogs salivated when they heard the bell which they previously associated with food, humans unconsciously associate a medical environment (for example doctors and medicine) with symptom relief and improved health. The reverse may also be true, however. If a patient has had bad experiences with physicians in the past, a “nocebo” effect, a negative or unpleasant reaction, may occur. The “expectancy theory” may also be a factor. In this case the patients’ expectations of improvement may affect the outcomes. Studies have shown that the expectancy theory may be due to the brain’s production of opiods called endorphines, which reduce pain by binding to the same receptor as morphine. Our pain-control pathways are linked with areas of the brain responsible for producing complex thought (the cortex) and emotion (the limbic system) and which then can be triggered by a person’s preconceptions. When given naloxone, a drug which blocks the effects of opiods, it has been shown to inhibit the placebo response in patients with expectations of improvement (1).


But are placebos dangerous? The placebo effect by itself is certainly not dangerous, after all what harm can a "sugar pill" do? Unless you have diabetes and take a lot of them. However the patients' health can be jeopardized if he or she totally believes in a certain placebo treatments, and refuses or delays getting treatments that are proven to have true clinical medical benefits.


In regard to placebo surgery, there exists an undeniable ethical dilemma which is the risk of harm a surgeon can cause his patient. For instance, in the case of a hip operation, the surgeon would cut a placebo patient up and then stitches it back up. Even if the doctor uses simple sedative instead of a full anesthesia, there are still great risks such as infection. Therefore, many surgical techniques used in placebo controlled trials would not be considered ethical.


Besides placebo surgery, there are other important ethical considerations for placebo drug trials even though less dramatic. For patients at risk of serious or long term harm such as depression, giving them inactive antidepressants is clearly not acceptable. In the case of cancer patients, to give them placebo radiology treatment or placebo chemotherapy is considered unethical since the disease could spread to other organs and become untreatable. When treating these patients, the researchers must continually watch the results in order to stop the study when there is evidence of significant improvement of either group.


However, placebo can be abused by nonscientific and unqualified healers. Although alternative medical practices like cleansing, homeopathy, healing ceremonies or prayers provide patients some comfort in a personal, caring way and give them some hopes, the empty placebo can become dangerous if the illnesses are life threatening like cancer or HIV.


According to Jonh E. Dodes (*), placebo can be harmful:

“Placebo responses can "teach" chronic illness by confirming and/or reinforcing the delusion of imagined disease (Jarvis 1990). Patients can become dependent on nonscientific practitioners who employ placebo therapies. Such patients may be led to believe they're suffering from imagined "reactive" hypoglycemia, nonexistent allergies and yeast infections, dental filling amalgam "toxicity," or that they're under the power of Qi or extraterrestrials.”

They are led to believe that diseases only yield to a specific type of treatment from specific practitioners, thus benefiting the healers. In convincing their patients that their conditions are only imagined, they, in turn, also believe the diseases are not real.


Is placebo unethical? This ethical concern may not be as big an issue if the practitioner truly believes in the treatment and that he or her does not benefit financially or professionally from his or her recommendations to the patients. Placebo can undermine the physician-patient relationship since it involves deception on the part of the doctor. Should the doctor use placebo without letting the patients know? Deceiving is unethical but the physician should resort to it to help relieve the sickness of the patients and to keep the effectiveness of the placebo.


The placebo effect is probably a result of a combination of many physiological as well as psychological mechanisms, but more research is needed to figure out how all these factors interact to produce the miraculous healing effect.



1) Stetka, Bret. Descartes’ Nightmare: The Convergence of Mind and Matter, and the State of Psychosomatic Medicine. April 16, 2007.

2) Nordenberg, Tamar. The Healing Power of Placebos. FDA Consumer Magazine, January, February 2000.

3) Henderson, Charles E.. Placebo Effects Prove the Value of Suggestion.

4) Pavlus, John. Mystery Painkiller. January 3, 2006.

5) Jeffrey, Susan. Functional MRI Helps Distinguish Belief, Disbelief, and Uncertainty. December 13, 2007.

6) Busko, Marlene. Placebo Effect Seems Related to Reward Expectations, Dopamine Activity. August 15, 2007.

7) Placebo Effect: Harnessing Your Mind’s Power To Heal. Science Daily, December 31, 2003.

8) Placebo Effect. Skeptic’s Dictionary.

9) Scott, D.J., Stohler, C.S., Placebo and Nocebo Effects are Defined by Opposite Opiod and Dopaminergic Responses. February 2008.

10) Wogan, Timothy, Are You Certain You Never Had a Placebo? First, July 17, 2007.

11) Dodes, John E., The Mysterious Placebo, Skeptical Inquirer magazine : January/February 1997

12) Barrett, S. 1977. Health frauds and quackery. FDA Consumer 11:12-17.

13) Jarvis, W. T. 1990. Dubious dentistry: A dental continuing education course. Loma Linda University, Loma Linda, Calif.