Placebo effects

I’m fascinated by placebo effects. Here are two recent topics that illustrate the power of placebo effects, and the challenge of interpreting whether drugs have the effects that are meant to have (over and above the placebo effect).

First, placebo effects getting stronger in clinical trials. This was reported in an article in Wired magazine, which also provides a wonderful survey of the bizarre world of placebo effects.  This is a world where the color, shape, and size of a sugar pill will influence its effectiveness, depending upon the medical condition being treated.  The problem with placebo effects getting stronger is that it becomes harder to determine whether the active medicine being tested is effective by itself.  Why is this strengthening happening?  The Wired article suggests that Americans are becoming ever more convinced by the power of drug companies to cure their ills.  I’m sure the companies appreciate this confidence in their skills.  They would probably appreciate all the more being able simply to sell sugar pills as treatments for our maladies.

The second example is a study of the effectiveness of anti-depressants in a recent issue of the Journal of the American Medical Association. The work shows (and builds upon lots of prior evidence) that both placebos and anti-depressants (two different drugs were tested:  paroxetine and imiprimine) improve people’s scores on a standard scale of depressive symptoms.  However, the drugs are better than placebo only for people with the most severe symptoms.  This study is discussed in a recent cover story in Newsweek by Sharon Begley.  Among the more interesting points is that even a positive effect of an antidepressant over placebo might itself be ascribed to a placebo effect.  Why?  Because people experience the side effects and hence figure that the antidepressant must be working, even if it is merely the power of suggestion having been triggered by the side effects.


About ethologist

Professor in the Department of Integrative Biology at Michigan State University
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