Abstract
BACKGROUND: Although placebo-control clinical trials that withhold effective treatments can be permissible, how best to inform participants of the placebo design has received little attention. AIMS: To determine the effect of disclosing quantitative outcome estimates of individual treatment v. entering placebo-control randomised control trial (RCT) on willingness to enrol in such an RCT. METHOD: We randomised 278 adult patients at a depression clinic to receive standard disclosure (n = 129) or enhanced (n = 149) quantitative outcome estimates (based on decision analysis) of individual treatment v. RCT, and assessed their willingness to enrol in the RCT. RESULTS: A greater proportion of those in the standard arm preferred enrolling in RCT (41.3% v. 23.8%, P = 0.002). Those in the standard arm preferred RCT more for direct benefit than altruism reasons, whereas the opposite was true in the enhanced arm. CONCLUSIONS: Disclosing the quantitative outcome implications of placebos may select for fewer but more altruistic participants. DECLARATION OF INTEREST: S.Y.H.K. was a DSMB member of a clinical trial sponsored by Hoffman-LaRoche and he receives royalties from Oxford University Press for his book Evaluation of Capacity to Consent to Treatment and Research. C.M. has served in the past year on a scientific advisory board and as a consultant for Janssen Pharmaceuticals. COPYRIGHT AND USAGE: This is an open access article distributed under the terms of the Creative Commons Non-Commercial, No Derivatives (CC BY-NC-ND) licence.