recently, researchers have unearthed significant flaws in this early research, leading some to doubt the very existence of the placebo response. Chapter Two sifts through the evidence to put together a picture of what placebos really can and can’t do. The interesting question is not whether placebos can alleviate medical problems – they can – but which medical problems they affect.
The list of medical conditions that respond to placebos is a rather odd one, without apparent rhyme or reason. Yet, as Chapter Three argues, there is in fact a single biological mechanism that is common to them all. If this mechanism is activated in all these medical conditions, it follows that placebos might work by turning this mechanism off. I may be wrong, and the placebo response may involve other mechanisms. If so, some of the predictions that follow from the model put forward here will not stand up to empirical test. That strikes me as a virtue rather than a disadvantage. Good theories, as the philosopher of science Karl Popper never tired of repeating, must be falsifiable. The bolder the conjectures, the more chances of being shown to be wrong, the better the theory. The theory put forward here is consistent with most, if not all, the data we currently have about the placebo response. But these are early days, and it is perfectly possible that scientists may discover further data that prove the theory wrong.
Such an event would not invalidate the whole book. Most of the arguments in its second half would still hold up even if the theory advanced in Chapter Three turns out to be wrong. Whatever the physiological details may be, for example, the important thing about placebos is that they cause their bodily effects indirectly, by means of causing some change in the mind. Chapter Four looks at the psychological element in the placebo response, the key mental event that triggers the physiological processes involved. I argue that this mental event is the formation of a belief – the belief that one has just received an effective medical treatment. Placebos are treatments that only work if you believe in them.
Chapter Five puts the physiological and psychological mechanisms in an evolutionary context. How and why did humans evolve in such a way that their minds can trick their bodies into healing themselves? When did this capacity first appear? Chapter Six examines the so-called ‘nocebo effect’ – the power of placebos to harm as well as to heal – and argues that this crude dichotomy into good and bad seriously misrepresents the complexity of the biological details. Since many symptoms turn out to be defence mechanisms activated by the body itself, it is much harder than one might think to decide whether or not a physiological process is pathological or beneficial.
Chapters Seven and Eight take a hard look at alternative medicine and psychotherapy, and ask whether or not these popular approaches to healing are really anything more than placebos. The question is especially important at a time when consumer demand for these products is high. Should we believe the hype surrounding acupuncture and homeopathy, or is the emperor naked?
Finally, Chapter Nine looks at the ethical questions raised by the use of placebos. To use a placebo knowingly, whether in medical practice or in clinical trials, it seems that doctors must deceive their patients. Can such deception ever be justified, or do doctors have an absolute duty to tell their patients the truth? And how do the emerging scientific discoveries discussed earlier in the book throw new light on this ancient dilemma?
That concludes the rough sketch of the terrain; now begins the journey.
Dylan Evans, Fairford, July 2002
PREFACE TO THE PAPERBACK EDITION
Since this book was first published, in January 2003, it has provoked a variety of responses, ranging from enthusiastic approval to cold hostility. This is probably to be expected, given that the book deals with a topic that is at the very edge of scientific discovery. Until we have gathered more evidence, scientists will continue to argue about the biological and psychological mechanisms that underlie the placebo response. Indeed, it is this process of argument and debate that makes science such a lively and passionate activity.
There are repeated reminders throughout the book that the theory proposed in Chapter 3 is not yet proven, but even this was not enough to prevent some critics from accusing me of presenting my hypothesis as if it were already an established fact. This is perhaps testimony to the reluctance of many medical scientists to venture beyond the safe realm of data and into the perilous terrain of theory. That reluctance is a shame, because speculation is essential if we are to discover anything new.
Recent research, published since this book was first published, appears to confirm the theory it proposes. Readers may find links to some of this research on my website (www.dylan.org.uk), which is regularly updated. But even if the theory proposed here turns out not to be a complete explanation of the placebo response, I am confident it will remain an important part of the puzzle. Read this book, and judge for yourself!
Dylan Evans, May 2003
In the closing years of World War II, while the Allies were fighting to liberate Europe from German occupation, morphine was in great demand at the military field hospitals. When casualties were particularly heavy, demand would outstrip supply and operations had to be performed without analgesia. On one such occasion, Henry Beecher, an American anaesthetist, was preparing to treat a soldier with terrible injuries. He was worried; without morphine, not only would the operation be extremely painful – it might even induce a fatal cardiovascular shock. But then something very strange happened, something that was profoundly to alter Beecher’s view of medicine for the rest of his life. In desperation, one of the nursing staff injected the patient with a harmless solution of saline. To Beecher’s surprise, the patient settled down immediately, just as if he had been given morphine. Not only did the soldier seem to feel very little pain during the subsequent operation, but the full-blown shock did not develop either.1 Salt water, it seemed, could be just as effective as one of the most powerful painkillers in the medical arsenal. In the following months, when supplies of morphine again ran low, Beecher repeated the trick. It worked. Beecher returned to America after the war convinced of the power of placebos, and gathered around him at Harvard a group of colleagues to study the phenomenon.
Around the same time, others were also beginning to take an interest in the placebo response. Harry Gold, at Cornell University, had been working on the topic independently since before the war. His work on angina had convinced him, like Beecher, that placebos could exert powerful therapeutic effects. In 1946, Gold led a discussion about the use of placebos in therapy at a conference at Cornell.2 Soon after, Beecher’s team at Harvard embarked on a series of studies comparing the effectiveness of analgesics with that of placebos. By 1955 interest in the placebo response had grown to such an extent that one of Beecher’s colleagues, Louis Lasagna, was even invited to write about the topic in Scientific American.3
The scientific interest in placebos was new. Although doctors had been quietly using sugar pills and water injections as sops to placate desperate patients for many years before Beecher started running his studies, few regarded the practice as worthy of serious research. Quite the contrary; physicians often felt rather uneasy about the whole business. It smacked of quackery and fraud. Doctors justified the practice of handing out placebos on the grounds that it could do no harm, but did not think for a moment that it actually helped patients to get better. An article in the Lancet in 1954 summed up this old-fashioned view of the placebo as ‘a means of reinforcing a patient’s confidences in his recovery, when
