• Julia Schmid, Nina Theysohn, Florian Ga, Sven Benson, Carolin Gramsch, Michael Forsting, Elke R Gizewski, and Sigrid Elsenbruch.
• Institute of Medical Psychology and Behavioral Immunobiology, University Hospital Essen, University of Duisburg-Essen, Essen, Germany Institute of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital of Essen, University of Duisburg-Essen, Essen, Germany Department of Neuroradiology, Medical University Innsbruck, Innsbruck, Austria.
• Pain. 2013 Nov 1; 154 (11): 2372-2380.

AbstractTo elucidate placebo and nocebo effects in visceral pain, we conducted a functional magnetic resonance imaging (fMRI) study to analyze effects of positive and negative treatment expectations in a rectal pain model. In 36 healthy volunteers, painful rectal distensions were delivered after intravenous application of an inert substance combined with either positive instructions of pain relief (placebo group) or negative instructions of pain increase (nocebo group), each compared to neutral instructions. Neural activation during cued-pain anticipation and pain was analyzed along with expected and perceived pain intensity. Expected and perceived pain intensity were significantly increased in the nocebo group and significantly decreased in the placebo group. In the placebo group, positive expectations significantly reduced activation of the somatosensory cortex during anticipation and of the insula, somatosensory cortex, and amygdala during pain delivery when compared to neutral expectations. Within the nocebo group, negative expectations led to significantly increased insula activation during painful stimulation. Direct group contrasts during expectation modulation revealed significantly increased distension-induced activation within the somatosensory cortex in the nocebo group. In conclusion, the experience and neural processing of visceral pain can be increased or decreased by drug-specific expectations. This first brain imaging study on nocebo effects in visceral pain has implications for the pathophysiology and treatment of patients with chronic abdominal complaints such as irritable bowel syndrome. Copyright © 2013 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

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