User:JohnHarmonPrice/Sandbox 2

The Concept of Placebo

It has been observed often enough, yet still frequently overlooked, that the notion of placebo as it occurs in modern clinical discourse is not a rigorous concept, and despite many attempts, it not been possible to provide a coherent definition. The most cited one is probably that of Arthur Shapiro<ref>The Placebo Response; in Modern Perspectives in World Psychiatry. Howells, J (Ed), 1968 and several subsequent revisions<ref>, which together with others in the same vein, makes use of the idea of "non-specific" therapeutic effects, and thus merely shifts the explanatory burden to this equally undefined concept. In addition, as Moerman has pointed out<ref>Meaning, Medicine, and the "Placebo Effect"; Cambridge, 2002<ref>, such definitions assert at the same time, that placebos are inert, and that they produce the placebo effect, which is self-contradictory. In a detailed critique of Shapiro's approach, Grunbaum attempted to formulate a logically consistent definition,<ref>Explication and Implications of the Placebo Concept; in Placebo: Theory, Research and Mechanisms. White, Tursky, Schwartz (Eds), Guilford Press, 1985<ref> but this in turn has been criticized on the grounds that not very informative. In the view of Moerman, Harrington, Kleinman and others, clinical science has burdened itself with a pseudo-concept, more confusing than useful, the correction of which will entail a revision of some foundational thinking in clinical medicine.

The following are some of the issues pointing to a fundamanetal problem:

• Ever since Beecher's 1955 study appeared, it has been claimed that about one third of the therapeutic effect observed in a typical trial is attributable to the placebo effect. But this is not what Beecher showed at all. In the "meta-analytic" section of his paper he gave the proportion of subjects across 15 trials deemed to have "been satisfactorily relieved by placebo" as 35.2% +/- 2.2%. This, if anything is an estimate of the frequency of 'placebo-responders' in the aggregate trial group, but says nothing about the magnitude of the effect.
• Beecher, intentionally or otherwise, gave currency to the idea that the placebo effects were roughly constant at around 35%, and that the term could be usefully applied to all those variables otherwise called "non-specific" contributors to therapeutic outcomes - the natural (and unknowable) course of diseases, regression to the mean, expectation effects, changes in affect and other unquantifiable psycho-somatic features of illness, beliefs and therapeutic communication, etc. If anything is clear from subsequent studies, it is that the placebo effect is not constant, but strikingly variable. Placebo response rates all the way from zero to 100% have been reported in virtually every clinical condition studied (the variation in Beecher's own series was 15-58%). The so-called effect appears to be both universal and utterly unpredictable.
• Beecher, who was concerned to promote the use of Randomised controlled trials (RCTs) in clinical research, made an unjustified assumption which is almost certainly false - that placebo effects in the intervention and control arms of a trial will be identical, or nearly so, and independent of the therapeutic effects. In the rationalization of RCTs which followed, this calim has never been rogorously defended, and in specific instances, can be easily refuted.⁴
• Kaptchuk has shown⁵ that both the name and the concept of placebo were transferred from at least 200 years of use in clinical practice, in the decade following the second world war, to a new role required by the methodology of what was then the new discipline of 'clinical research'. Earlier usage corresponded to its Latin etymology - a harmless pill or potion given knowingly to patients who were either hard to please or hard to cure. The first clear example cited in the OED is from 1811. But during the post-war therapeutic revolution, it became the wastebin into which all the confounding factors that disturb therapeutic assessments were tipped. In Beecher's terms, it became a powerful if enigmatic distraction to researchers, who's results would be contaminated without rigorous procedures for its exclusion. Its modern use is therefore quite recent, and closely related to the adoption of the RCT as the methodological gold standard for trials of therapy.
• A considerable body of work has attempted to elucidate the 'mechanism' of the placebo effect - but without much success. Proposals ranging from 'suggestibility' and various other psychological hypotheses, to neuro-endocrine studies, and attribution of the effect to statistical artefacts, have turned out to be flawed in various ways, so that clinical researchers have no more idea of what is really going on the control arms of their trials than did Hippocrates. It seems unlikely that this deeply unsatisfactory situation will be resolved by a new attempt to answer the old question; instead, as has been suggested by some of the most thoughtful students, we should expect to find that some part of the conceptual landscape in which this problematic entity resides must be reconstructed before it will come into focus. This view commends itself specially to those scholars who bring to the problem a perspective from outside the clinic - from medical anthropology, history of medicine, philosophy, and statistics.⁶