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Neurogastroenterol Motil. 2012 Oct;24(10):935-e462. doi: 10.1111/j.1365-2982.2012.01968.x. Epub 2012 Jul 2.

Perceived treatment group affects behavioral and neural responses to visceral pain in a deceptive placebo study.

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1
Institute of Medical Psychology and Behavioral Immunobiology, University Hospital of Essen, University of Duisburg-Essen, Essen, Germany.

Abstract

BACKGROUND:

To assess effects of perceived treatment (i.e. drug vs placebo) on behavioral and neural responses to rectal pain stimuli delivered in a deceptive placebo condition.

METHODS:

This fMRI study analyzed the behavioral and neural responses during expectation-mediated placebo analgesia in a rectal pain model. In N = 36 healthy subjects, the blood oxygen level-dependent (BOLD) response during cued anticipation and painful stimulation was measured after participants were informed that they had a 50% chance of receiving either a potent analgesic drug or an inert substance (i.e., double-blind administration). In reality, all received placebo. We compared responses in subjects who retrospectively indicated that they received the drug and those who believed to have received placebo.

KEY RESULTS:

55.6% (N = 20) of subjects believed that they had received a placebo, whereas 36.1% (N = 13) believed that they had received a potent analgesic drug. Subjects who were uncertain (8.3%, N = 3) were excluded. Rectal pain-induced discomfort was significantly lower in the perceived drug treatment group (P < 0.05), along with significantly reduced activation of the insular, the posterior and anterior cingulate cortices during pain anticipation, and of the anterior cingulate cortex during pain (all P < 0.05 in regions-of-interest analyses).

CONCLUSIONS & INFERENCES:

Perceived treatment constitutes an important aspect in placebo analgesia. A more refined understanding of individual treatment expectations and perceived treatment allocation has multiple implications for the design and interpretation of clinical trials and experimental studies on placebo and nocebo effects.

[Indexed for MEDLINE]

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