Book of the Month: Placebo: The Belief Effect
Authors: Annabelle Mark
Journal: Journal of the Royal Society of Medicine (2003)

Placebo may have been the mainstay of medical practice until the 20th century, but how it works and what role it plays in the current research culture is only now being investigated. In Placebo: the Belief Effect1—a very lively exploration of the role of placebo in the development of medicine and its more recent use as a key tool of medical research—Dylan Evans shows us how little is still known, and furthermore casts considerable doubt on those who have so far professed to understand it. He then goes on to review new findings on the molecular linkage between brain and immune system that might lie behind the effect. This occurs, he suggests, through suppression of the acute phase response as revealed in such signs as pain, inflammation, swelling and fever. The science is set out in some detail, but this is not just a book for doctors and researchers; the use of engaging examples makes much of it enjoyable reading for those not medically qualified.

Evans begins by recounting the circumstances in which placebo emerged, with a penetrating critique of Beecher's seminal work published in JAMA in 1955. Although bad science, he says, makes bad practice, it can still yield important pointers for further research. Looking at progenitors of the clinical trial he tells of an experiment conducted by Frederick II in Sicily in the 13th century. To see how exercise affected the digestion, the King gave two knights a meal, then sent one to bed and the other out hunting. What they were probably not told was that he would kill them to compare the contents of their alimentary canals. Some progress has been made since then, principally in the 20th century with the use of randomization and the placebo control. For the non-medical reader it is unfortunate that not until nearly half way through the book are we offered an explanation of standard research practice—e.g. setting out the difference between blind and double blind. By this point Evans has treated us to an array of research examples in support of his arguments. In chapter 2 we read of Shapiro's work indicating differential effects of pill colour on treatment outcomes—an observation that should have been of great interest to the pharmaceutical industry. His exploration of current research methods also points to design weaknesses, especially if we accept his theory that placebo suppresses immune responses; comparisons of placebo with ‘no treatment’ might be enlightening if ethically acceptable.

Evans' analysis points to the influence of external environmental factors on body—brain interactions, and we see possible mechanisms for both the ‘doctor-effect’ described by Balint2 and the benefits reported by patients from alternative and complementary therapies. (These benefits are acknowledged by British general practitioners: by the year 2000 more than half were providing direct access to such services.) What is less clear in the book is what one might call the boundary of belief—the extent to which any intervention must be consciously perceived for it to be effective. As he says, ‘with most brain processes... the goal of conceptual integration is still a long way off in practice’. Damasio3 would agree. While there is some discussion of this point, together with the ethical restrictions now placed on research, it may be that the most effective way to determine these boundaries will be through working with groups who so far have received little attention—old people, those with mental illness, or children. Until quite recently babies were perceived to have low sensitivity to pain, and treated accordingly, because doctors laid importance on cognition rather than the evolutionarily older sensory systems. Evans believes that the historical evolution of different aspects of the human body offers a way to fill gaps in knowledge of the placebo response—notably, immune reactions of various evolutionary ages, and their consequences.

A whole chapter is devoted to the power of belief and its effects on physiology, highlighting the possible differences between individuals, however well matched they are in statistical terms. What the book does not discuss is the conflict between such personal characteristics and evidence-based medicine (EBM), which depends on observations in groups rather than individuals.4 Evans' analysis suggests that there are ‘complex ways in which people come to believe their treatment will be effective, sometimes putting the evidence of their senses above the voice of authority, while at other times doing completely the opposite’. Many within the medical profession continue to be guided by similar instincts, describing their thought processes as clinical judgment. It is issues of this sort that have made EBM so hard to implement. As discussed in chapter 5, a dampening effect of placebo on the acute phase response could be interpreted as reflecting the uniquely human social expectation of care from others.5 Perhaps the most intriguing part of the book, coming from this former psychotherapist, is the exploration of the role of psychotherapy. His conclusion is that, even if psychotherapy proves to be no more than placebo, this does not necessarily detract from its usefulness; and, if it is better than placebo, our failure to understand how it acts on the brain may be analogous to our ignorance of exactly why certain drugs are effective. Evans is at his best when writing from personal experience. Whatever the reader's conclusions about the scientific arguments, his examples and delivery provide a thoroughly engaging way into this debate.