Controls, Belief Updating, and Bias in Medical RCTs

Gilles Chemla and Christopher A. Hennessy
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Gilles Chemla: DRM - Dauphine Recherches en Management - Université Paris Dauphine-PSL - PSL - Université Paris Sciences et Lettres - CNRS - Centre National de la Recherche Scientifique

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Abstract: We develop a formal model of placebo effects. If subjects in seemingly-ideal single-stage RCTs update beliefs about breakthroughs based upon personal physiological responses, mental effects differ across medications received, treatment versus control. Consequently, the average cross-arm health difference becomes a biased estimator. Constructively, we show: bias can be altered through choice of control; higher-efficacy controls mitigate upward bias; and efficacy states can be revealed through controls of intermediate efficacy or controls that mimic a subset of efficacy states. Consistent with experimental evidence, our theory implies outcomes within-arm and cross-arm differences can be non-monotone in treatment probability. Finally, we develop novel differences-in-differences and triangle equality tests to detect RCT bias

Keywords: Medical randomized controlled trials; Treatment; placebo effects (search for similar items in EconPapers)
Date: 2019
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Citations: View citations in EconPapers (4)

Published in Journal of Economic Theory, 2019, 184, ⟨10.1016/j.jet.2019.07.016⟩

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Persistent link: https://EconPapers.repec.org/RePEc:hal:journl:hal-03342440

DOI: 10.1016/j.jet.2019.07.016

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