The clinical relevance of placebo

Evidence from clinical studies emphasizes the relevance of contextual psychosocial variables, including physicianpatient interactions, for treatment outcome [1]. Positive psychosocial infl uences on treatment outcomes are termed placebo eff ects, whereas negative infl uences are termed nocebo eff ects. Experimental research reveals that the psychosocial context of therapy induces biochemical changes in the brain and body and that these changes may aff ect the natural history of a disease and the response to a treatment [2,3]. Along these lines, negative responses to drugs have been shown to be much better predicted by the patient’s individual beliefs and negative expectations regarding a drug’s eff ect (nocebo eff ects) than by the specifi c pharmacological properties of the drug [4] itself. Placebo and nocebo eff ects are therefore centrally impor tant in medical practice, whether these are intentionally used by health-care practitioners or not. A more widespread recognition of this fact may enable and encourage patient-physician interactions that are conducive to positive treatment outcomes. Such interactions are important in determining a number of factors that may aff ect outcome, including patients’ mood, their concepts of disease, treatment expectations, and their willingness to endure therapeutic side eff ects. However, this knowledge should be taken in the context of the observation that, in the US, 50% of patients leave after a visit with their doctor without an adequate understanding of what the doctor has told them [5]. Th erefore, there is clearly an opportunity for improv ing therapeutic responses to current treatments and a need for more research into and greater under standing of what factors aff ect those responses. Until recently, placebo analgesia has been regarded as a nuisance phenomenon in clinical trials. Th is has shifted to the idea that studying placebo eff ects allows us to gain insight into the mechanisms of the endogenous control of pain. Research over the last few decades has improved our understanding of the neuropsychology and neurobiology that underlie placebo and nocebo eff ects. Th ese insights have potentially far-reaching implications for future research and clinical practice. Further understanding of these mechanisms may aid in predicting which contexts (physiological, psychological, and social) have the greatest potential for inducing positive treatment responses. Th is may help to improve the design of clinical trials. It may also help to understand treatment mechanisms by allowing the separation of drug-specifi c responses from non-specifi c (contextually mediated) responses. Th is article is aimed at providing an overview for clinicians of the importance of contextual variables in determining treatment response, and the specifi c focus is on placebo response. We will examine psychological Abstract