Context effects. Powerful therapies or methodological bias?

This article provides an analysis of the way in which placebo effects could be investigated and taken into account, supported by a description of some of the major articles that have been published on this topic. Based on conceptual, theoretical, and methodological issues, the authors highlight some of the reasons for current controversies regarding the nature of placebo effects. They suggest the use of the term context effects to overcome some of the negative connotations associated with the term placebo and to highlight the therapeutic nature of the health care context, and they present the major findings and limitations from their systematic review of the therapeutic effects of health care interactions. Recommendations for future research are proposed.