The Placebo Effect: How Strong Is The Power of Suggestion?

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Biology 202
2002 First Paper
On Serendip

The Placebo Effect: How Strong Is The Power of Suggestion?

Cassidy Garrison-Kimmel

For years, scientists have sought to find an explanation for the placebo effect. Although many hypotheses exist, there is no one reason defining why or how the placebos work. Some researchers argue that the phenomenon doesn't even occur; that the placebo effect is merely random error and that any improvement said to be caused by a placebo is simply a spontaneous recovery in the patient's condition (2)(3). Other scientists argue that Pavlovian conditioning supports an explanation for the effect: If patients have previously shown improvement from being in a medical setting or from taking medicine, they are conditioned to experience positive effects every time they are in the same situation (1). A second explanation for the placebo effect is that any drug (or placebo) given to a patient will reduce their stress levels. Because many illnesses begin under high-stress circumstances, or exhibit more extreme symptoms under stressful situations, many of the patient's symptoms are likely to improve (2)(4).

The first question that must be answered before delving into the hypotheses behind the placebo effect is whether or not the phenomenon even exists. Certain physicians and scientists claim that "positive effects" of a placebo are, in actuality, just the body's natural ways of healing itself and the immune system's defenses kicking in soon after the placebo is taken (2). Basically, these researchers argue that improvement in a patient's condition after being administered a placebo is merely a coincidence. Negative effects that are often blamed on placebos are viewed by these researches in the same way: nausea or headaches that are claimed to be a placebo's side effects may be spontaneously occurring symptoms (3).

It has been established that colds, nausea, headaches and flus will indeed go away eventually, regardless of whether we take drugs or not. But how can studies that show that placebos have an effect on more serious and chronic illnesses, or potentially fatal conditions, such as hypertension, asthma, Parkinson's disease and schizophrenia be explained?

One theory comes from Pavlov's experiment on conditioned reflexes. In this experiment, Pavlov rang a bell before giving food to a dog. After a numerous trials, no food was given after the bell rang, but the dog still salivated and expected the food. This reflex was an involuntary bodily response to an outside stimulus. Similarly, many people have experienced relief after visiting a physician or taking a medication. Therefore, the patient would be conditioned to respond positively to any visit to a physician's office or any medication administered to them, even if that medication is a placebo (1). This is where the strength of suggestion comes into play-- if the physician tells the patient that the medication is a drug that will help the patient's condition, and if the patient has been previously conditioned as mentioned above, then the patient's body will respond accordingly in about 50-60% of all the cases (3)(4). The number of cases in which the placebo causes positive, healing effects sometimes even exceeds the number of cases in which the actual drug does the same (4).

Another theory behind the placebo effect has to do with the placebo and positive suggestions from the physician reducing stress levels in the patient. Many ailments are at least partially stress-related, including hypertension, asthma and panic and anxiety disorders. According to the scientists who subscribe to this theory, stress can impair the immune and endocrine systems (5). Being removed from an environment which a patient associates with illness and being placed in a different environment which is commonly associated with healing, such as a physician's office or a hospital, can immediately reduce the patient's stress level. This means that placebos are not always in the form of medicines, and that merely changing environments can trigger the placebo effect (5). Also, the reassurance from a physician that the patient will feel better immediately reduces stress. The theory that stress reduction is responsible for the placebo effect can be likened to the Pavlovian conditioning theory, in that the change of environment or positive reassurance from the doctor acts as a stimulus. The conditioned response to the stimulus would be a lowered stress level.

Contrary to what some scientists argue, the placebo effect does seem to exist, according to numerous studies conducted throughout the past century. I am curious about why doctors don't prescribe placebos more often since there is so much data supporting their positive effects. Are doctors just too anxious to prescribe drugs, or is there an ethical reason behind it? Although scientists can't agree on the explanations behind the placebo effect, I think it is obvious that the body is very susceptible to the power of suggestion. Does it matter why the placebo effect occurs, as long as its consequences are positive?


1) Placebo Effect: The Power of the Sugar Pill

2) Scientific American; All In The Mind by W. Wayt Gibbs

3) Placebos

4) The New York Times Magazine; The Placebo Prescription by Margaret Talbot

5) Hospital Practice; Harnessing The Placebo Effect by Miroslav Backonja and Walter A. Brown

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