Nocebo effects in health psychology

The nocebo effect is a potentially powerful phenomenon that can result in harmful or unpleasant treatment outcomes caused by negative expectations, past experience, and other aspects of the treatment context. These aversive outcomes can cause patients to discontinue an otherwise beneficial treatment-resulting in suboptimal health outcomes, added burden of illness, reduced quality of life, and unnecessary hospitalisations, medical consultations, and increased cost for both the patient and the health care system. Much research to date has focused on the role of negative expectations in nocebo effects; this review also emphasises the more overlooked mechanisms of anxiety and classical conditioning, and how these might be usefully targeted to reduce nocebo effects. The evidence for each of these mechanisms, and their potential interactions, is reviewed. Regardless of how they develop, nocebo effects can contribute substantially to the overall burden of treatment side effects, and an overview of evidence-based interventions to reduce nocebo effects by targeting each of the underlying mechanisms is presented. Currently, no strategies are systematically applied to reduce nocebo effects, and most interventions have yet to be translated from experimental laboratory research into applied clinical settings. Future work should focus on developing and testing theoretically-based interventions to reduce nocebo effects, and on translating findings from lab-based studies into clinical practice and healthcare policy.