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PLoS One. 2012;7(10):e48135. doi: 10.1371/journal.pone.0048135. Epub 2012 Oct 23.

Catechol-O-methyltransferase val158met polymorphism predicts placebo effect in irritable bowel syndrome.

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  • 1Division of General Medicine and Primary Care, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, United States of America. kthall@bidmc.harvard.edu

Abstract

Identifying patients who are potential placebo responders has major implications for clinical practice and trial design. Catechol-O-methyltransferase (COMT), an important enzyme in dopamine catabolism plays a key role in processes associated with the placebo effect such as reward, pain, memory and learning. We hypothesized that the COMT functional val158met polymorphism, was a predictor of placebo effects and tested our hypothesis in a subset of 104 patients from a previously reported randomized controlled trial in irritable bowel syndrome (IBS). The three treatment arms from this study were: no-treatment ("waitlist"), placebo treatment alone ("limited") and, placebo treatment "augmented" with a supportive patient-health care provider interaction. The primary outcome measure was change from baseline in IBS-Symptom Severity Scale (IBS-SSS) after three weeks of treatment. In a regression model, the number of methionine alleles in COMT val158met was linearly related to placebo response as measured by changes in IBS-SSS (p = .035). The strongest placebo response occurred in met/met homozygotes treated in the augmented placebo arm. A smaller met/met associated effect was observed with limited placebo treatment and there was no effect in the waitlist control. These data support our hypothesis that the COMT val158met polymorphism is a potential biomarker of placebo response.

PMID:
23110189
[PubMed - indexed for MEDLINE]
PMCID:
PMC3479140
Free PMC Article

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