Abstract

Often regarded simply as a nuisance in clinical drug trials in which the aim is to separate drug response from placebo response in a statistically significant manner, the placebo response has important implications. These implications relate to the nature of illness, the study of non-specific factors in the treatment setting that are related to clinical improvement, methods of enhancing these non-specific sources of benefit, and the neurobiology that is associated with the placebo response. Specific sources of clinical improvement in medical and psychological treatment generally consist of drugs or clear interventions that appear to directly contribute to the desired treatment. Non-specific factors, on the other hand, include the clinician–patient relationship, installation of hope, relationship with authority, and other such factors that are more implicit to treatment and may contribute to the placebo response. Our understanding of how these non-specific aspects of treatment relate to clinical improvement and ways of enhancing these non-pharmacological elements of therapy may form important aspects of treatment. Furthermore, an important, albeit potentially overlooked element of the placebo response are clinical-trial designs and methodologies, themselves. Specific neurobiological changes also appear to be associated with the placebo response in at least some cases. Finally, it is suggested that the placebo response may in some instances represent a type of brain plasticity in which expectation and desire — agency — can result in specific changes in brain function that either may mirror or differ from the effects of certain drugs