The powerful placebo: from ancient priest to modern physician

Many historians have used the placebo effect, alongside remission and self-limiting ailments, as a catch-all explanation for apparent cures in the past, whether at the hands of doctors or saints, but they have rarely exhibited much awareness of its ubiquity and potential scale or considered what behaviour and beliefs promote it. Since the business of historians lies mainly with beliefs and the changing social circumstances of healing practices, rather than with the mechanical efficacy of medical techniques, the placebo effect needs to be taken rather more seriously, as the major determinant of successful healing throughout history. A careful reading of these two books should help to ground historians' assertions more securely and provide new avenues for research. The late Arthur Shapiro, a clinical psychologist, spent his career examining the effects associated with placebos, a little understood phenomenon when he began. The powerful placebo, completed by his widow, summarizes his own research and that of his colleagues, and attempts to provide the historical context. The placebo effect, edited by the historian Anne Harrington, brings together some of the leading authorities to describe the state of the field, as it appears from their several disciplinary perspectives, and to outline future directions for research. Although there has always been an undercurrent of interest in the effects of the imagination on health and illness, this has run contrary to the dominant traditions of modem Westem medicine, which has increasingly concentrated on the application of specific cures for specific ailments. The placebo effect has therefore been marginalized, as something to be eliminated in drug trials or as an accusation made against other medical groups. Shapiro provides useful narrative accounts of the technical and ethical issues in the development of double-blind trials. He also provides a valuable analysis of the impossibility of designing double-blind trials for either surgical procedures or psychotherapeutic methods. This has enabled surgeons and psychotherapists to imagine that their fields are unaffected by the placebo effect, whereas it has long seemed that these are the areas in which its force is greatest. Readers who have yet to be convinced of the importance of the placebo effect should certainly read Shapiro's book, where the evidence is marshalled exhaustively, but without modish hyperbole. Since the phenomenon includes both positive and negative reactions to health care, it is clear that the potential range of variation between nonspecific benefits and non-specific harm is vast. Shapiro has little to say about the negative side of the placebo effect, sometimes referred to as the "nocebo effect" or "voodoo death", but this controversial topic is carefully considered in an essay by Robert A Hahn. Shapiro is weak on causal mechanisms, whether psychosocial or neurological. He exhibits little interest in Pavlovian conditioning and is hostile to the burgeoning field of psychoneuroimmunology, although he has no difficulty in accepting that the endocrine system, for example, is affected by psychological states. The essays in The placebo effect address this problem in several ways. As Robert Ader insists, conditioning must form part of any explanation and the conditioned response has great potential utility in the clinical situation, for combating dependence and toxicity in long-term drug regimes. However, the response to placebos is not uniform, so the neurobiology of placebo analgesia, examined by Howard L Fields and Donald D Price, cannot be generalized to placebo tranquillizers, for example. Although he is very present-minded, dismissing all drug therapies before the