• Lisa A Conboy, Rachel H Wasserman, Eric E Jacobson, Roger B Davis, Anna T R Legedza, Min Park, Andrea L Rivers, Elizabeth B Morey, Bong Hyun Nam, Louis Lasagna, Irving Kirsch, Anthony J Lembo, Ted J Kaptchuk, and Catherine E Kerr.
• Osher Institute, Division for Research and Education in Complementary and Integrative Therapies, Harvard Medical School, 401 Park Drive, Suite 22A, Boston, MA 02115, USA.
• Contemp Clin Trials. 2006 Apr 1; 27 (2): 123-34.

AbstractLittle is known about placebo effects with scientific precision. Poor methodology has confounded our understanding of the magnitude and even the existence of the placebo effect. Investigating placebo effects presents special research challenges including: the design of appropriate controls for studying placebo effects including separating such effects from natural history and regression to the mean, the need for large sample sizes to capture expected small effects, and the need to understand such potential effects from a patient's perspective. This article summarizes the methodology of an ongoing NIH-funded randomized controlled trial aimed at investigating whether the placebo effect in irritable bowel syndrome (IBS) exists and whether the magnitude of such an effect can be manipulated to vary in a manner analogous to "dose dependence." The trial also uses an innovative combination of quantitative and qualitative methods.

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