The May 24, 2001 issue of the New England Journal of Medicine
carried two pieces questioning the effectiveness of the placebo in certain circumstances. The main article was a study titled "Is the Placebo Powerless?
— An Analysis of Clinical Trials Comparing Placebo with No Treatment" and was conducted by Dtch researchers A. Hrobjartsson
and P. C. Gotzsche
. There is also an editorial, The Powerful Placebo and the Wizard of Oz
J. C. Bailar III
I don't have access to the text of the study, but the Journal of the American Medical Association reports that the study was a survey of clinical drug trials in which there were both placebo and no treatement control groups, and compared the effectiveness of those two courses of action. What they found, apparently, was that for most of the 114 studies cited, there was little or no benefit to taking placebos over avoiding treament altogether. The summary continues,
"Placebos did appear to produce small benefits in studies in which the outcome being measured was subjective and continuous, and in trials of pain treatment."
Now, while this clearly warrants further investigation, it is not quite a damning condemnation of the classical notion of the placebo effect. The vast majority of clinical drug trials don't include both placebo and zero treatment control groups; and a good many studies these days don't include a placebo group at all -- often new drugs are compared to a control group that uses an existing treatment regime, for obvious ethical reasons. I believe I read a news item when the study was published that the researchers had to wade through over 8,000 studies to find the 114 they analyzed for their work. We cannot, therefore, assume that the coverage of study was broad or comprehensive. This is the normal process of science; while popular media likes to make strong statements about the results of this study or that, careful science takes small, measured steps, preferring a strong degree of confidence in a small step over a weak degree of confidence in a bold sweeping conclusion.
Certainly the placebo effect has been the subject of study before, and in the end a thorough discrediting of the placebo effect will have to come up with a well-documented and careful explanation for those results, either through methodological analysis of past studies or by finding a balance between the ideas that the placebo effect is huge and that the placebo effect doesn't work.