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RESEARCH ARTICLE
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- Published: Nov 18, 2013
- DOI: 10.1371/journal.pone.0079576
Abstract
Background
Placebo effects have been reported in type I allergic reactions. However the neuropsychological mechanisms steering placebo responses in allergies are largely unknown. The study analyzed whether and to what extend a conditioned placebo response is affecting type I allergic reactions and whether this response can be reproduced at multiple occasions.
Methods
62 patients with house dust mite allergy were randomly allocated to either a conditioned (n = 25), sham-conditioned (n = 25) or natural history (n = 12) group. During the learning phase (acquisition), patients in the conditioned group received the H1-receptor antagonist desloratadine (5mg) (unconditioned stimulus/US) together with a novel tasting gustatory stimulus (conditioned stimulus/CS). Patients in the sham-conditioned control group received the CS together with a placebo pill. After a wash out time of 9 days patients in the conditioned and sham-conditioned group received placebo pills together with the CS during evocation. Allergic responses documented by wheal size after skin prick test and symptom scores after nasal provocation were analyzed at baseline, after last desloratadine treatment and after the 1st and 5th CS re-exposure.
Results
Both conditioned and sham-conditioned patients showed significantly decreased wheal sizes after the 1st CS-evocation and significantly decreased symptom scores after the 1st as well as after the 5th evocation compared to the natural history control group.
Conclusions
These results indicate that placebo responses in type I allergy are not primarily mediated by learning processes, but seemed to be induced by cognitive factors such as patients’ expectation, with these effects not restricted to a single evocation.
Figures
Citation: Vits S, Cesko E, Benson S, Rueckert A, Hillen U, et al. (2013) Cognitive Factors Mediate Placebo Responses in Patients with House Dust Mite Allergy. PLoS ONE 8(11): e79576. doi:10.1371/journal.pone.0079576
Editor: Antonio Verdejo García, University of Granada, Spain
Received: April 26, 2013; Accepted: September 23, 2013; Published: November 18, 2013
Copyright: © 2013 Vits et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: This study was supported by the Volkswagen Foundation (I/83 806) (http://www.volkswagenstiftung.de)and the German Research Foundation (DFG) (Sche 341/17-1) (http://www.dfg.de). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
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