The Placebo Effect part I: The real deal?

Posted on August 27, 2007
Filed Under Science |

Since it was first proposed in 1955, the placebo effect, which can be defined as a pseudo-treatment from which patients appear to get better has intrigued scientists.

An example of such an effect occurs with pain perception. Physicians and scientist believe that the placebo effect with respect to pain is dependent on the attitude and belief of a patient. That is, that the patient has an expectation of relief when they believe they are receiving an effective treatment, which allows them to feel relief regardless of whether the treatment given is real or not (the placebo effect with pain).

On the other hand, some researchers have argued that the placebo effect has been largely misrepresented in research studies due to things like response bias (participants in a study act in a manner to please the people running the study regardless of there true beliefs). Therefore, the question whether this placebo effect exists or not and could this truly be proven has been a debatable question in the scientific community.

It gets more complicated by evidence suggesting that the placebo effect can be reversed by inhibiting the opioid system (a system in which a morphine like action is produced in the body-relieving pain) with the drug naloxone, however, studies have since shown that naloxone can cause pain relief independent of placebo. Recently, Dr. Tor D. Wager of the University of Columbia, while working at the University of Michigan has given support for the existence of the placebo effect. Given that pain and pain perception are interpreted in the brain, if placebo-induced changes can occur, it would seem that they would occur in regions associated with sensory and pain processing function in the brain, if these could be monitored, particularly over time (a time course in which pain occurs), this may provide insight into the placebo effect.

Dr. Wager used functional magnetic resonance imaging (fMRI) to analyze the brains of 47 individuals split into two studies. One of the major arms of the study had individuals told they were participants in the evaluation of an analgesic cream that would reduce but not eliminate pain. Some individuals were given the cream (placebo) and some were not. Electric shocks were applied to the wrist of both individuals (this in order to determine if brain activity with pain could be detected) given the analgesic cream and those not given the cream, with a warning that the upcoming shock would be intense or mild. In the other arm of this experiment, participants were told that shocks would occur at a higher threshold level than what was actually administered, (to determine what specific areas of the brain registered activity), the brain regions were mapped and a time course was generated to determine where and when brain activity occurred.

Individuals in the study reported that they felt more relief when the cream was administered than those who did not receive the cream on average, these individual reports of decreased pain due to the application of the analgesic cream correlated with decreased brain activity in the pain-mapped areas. In addition, similar placebo effects were seen with individuals who thought they were receiving an increased amount of electric shock when in fact they were receiving a moderate to mild shock. Wager and colleagues from this study were able to make two important findings 1) the placebo effect does exist and 2) that a placebo decreases pain responses to areas of the brain that are associated with pain.

Related: The Placebo Effect Part II: There’s always a but….

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