The influence of the nocebo effect in clinical trials

Luana Colloca<sup>1,2,3

1</sup>National Center for Complementary and Alternative Medicine, National Institutes of Health, Bethesda, MD, USA; ²National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA; ³Department of Bioethics, The Clinical Center, National Institutes of Health, Bethesda, MD, USA

Abstract: Neurobiological and clinical studies have shown that learning mechanisms and expectations of benefits powerfully affect the brain, mind, and body, with the potential of relieving many symptoms during the course of daily clinical practice. Playing the role of antagonist is the "nocebo effect," which results from negative expectations derived from one's beliefs, previous experiences, and his or her clinical encounters that produce negative effects. Research on the nocebo effect indicates that information disclosure and the manner in which information is delivered can contribute to these adverse effects. In this article, we review neurobiological and medical studies relating to the nocebo effect, as these findings are important for the methodology of clinical trials.

Keywords: adverse events, clinical research, communication, expectation, nocebo effects, side effects