For a long time the book about placebo effect was Placebo: theory, research and mechanisms, edited by L White, B Tursky, and G E Schwartz (1985). It remains interesting because of the many thoughtful and detailed chapters about definition, mode of action and ethics. In 1997 three books on the subject appeared (see reviews in Medical History, 1999, 43: 124−5 and 269−70) that showed how complex the field is. I think many people who have followed the discussions about placebo and placebo effect now expected a pause for thought: what are we talking about when we say placebo effect? Is there a definition of placebo effect we can agree upon? Should we simply leave the concept of a placebo effect? Is it too complex and too much of a “garbage can”? In the last two years an astonishing number of popular and scientific books about placebo effect have been published or republished by authors such as Howard and Daralyn Brody, Harry A Guess, et al., Lolette Kuby, Daniel Moermann, David Peters (ed.), and Howard Spiro.
One of the newest books that is based on new knowledge in the field, and also aimed at a broader public, is Dylan Evans' Placebo: the belief effect. The author has a “middle of the road” standpoint between the more extreme views that placebo effects do not have any clinical importance and that placebo effects have a big influence on many symptoms that can be seen in daily medical practise. According to Evans, placebos work on a limited range of conditions like pain, inflammation and depression but not on infections, chronic degenerative diseases or cancer. He claims that placebo-responsive conditions all involve acute phase responses. These are responses in the body that involve pain, swelling, fever, lethargy, apathy, etc., often less technically called “inflammation”. Evans argues that these reactions of the body and its innate immune system are not pathological but part of the healing process. The mechanism that turns off the acute phase response sometimes malfunctions and persists too long. So the placebo effect, or belief effect as Evans prefers to call it, should work by suppressing overdue activities in the body. The patients' beliefs play an important role in activating the placebo effect, and they can be influenced by information from other people, experience or logical thinking.
An overall explanation of all placebo effects has been shown to be problematic, and Evans admits that this hypothesis cannot explain everything and is merely speculative. But in arguing for his hypothesis he brings the reader on a well guided tour through much literature on immunology, psychology, psychotherapy, alternative medicine, ethics, etc. He also raises the question of whether placebo effects are always good since they suppress activities that normally are supposed to be healthy for us. Something that makes us feel good is sometimes bad for us and vice versa.
The book is very well written, it touches a lot of relevant corners of the debate and tries to put up a new hypothesis about placebo effects. What more can one expect? The historically interested might look for better introductions to placebo/placebo effect elsewhere. Evans writes that from the Second World War everything changed; from being a pious fraud, now placebo was supposed to heal people. Did everything really change here? I doubt it. In the nineteenth century also some physicians believed placebos could relieve symptoms, and after the Second World War many physicians were sceptical of the effect and the practice of giving placebos. There is much more to the developments of the last 200 years than a simple before and after the war.
Also from an historical point of view it is interesting that there is still no agreement upon how important the placebo effect is and how to define it. There seem to be at least two different perspectives. One is that placebo effects have to do with placebos and can be investigated through research into the effect these have on groups of patients compared with treatment- or no-treatment-groups. This perspective has a fifty-year long tradition. The other is that placebo effects come from the mind's influence upon the body. This perspective has a 2000-year long tradition. These two traditions have different points of view and a mapping of this controversy could be interesting. Evans does not do this, but that would perhaps be too much to expect from one book.
It is a good book, but the competition in the field is fierce. Those interested in the subject who would like to read some of the newest books in the field should also consider Daniel Moerman, Meaning, medicine and the ‘placebo effect’ (2002) and Harry A Guess, et al., The science of the placebo (2002).
