Factors affecting placebo acceptability: deception, outcome, and disease severity.

UNLABELLED: A burgeoning body of evidence supports the efficacy and elucidates the mechanisms of placebo analgesia. Debate persists, however, concerning their ethical use, with many of the present arguments being philosophically based. The present web-based study empirically investigated the acceptability of an analgesic placebo treatment. Participants (103) responded to vignettes depicting patients receiving a placebo analgesic. We experimentally manipulated: 1) placebo treatment instructions (level of deception); 2) treatment outcome; and 3) patients' pain severity. Participants rated vignettes on outcome measures of deception, physician-patient relationship, and patient mood. Participants then characterized a range of placebo acceptability through ratings of deceptiveness, effectiveness, and negative consequences. Results showed that placebos described as "medication shown to be a powerful analgesic in some people" were equally deceptive as those described as "standard drug treatment." Ratings of patient mood and physician approval were determined as much by treatment instruction as by treatment outcome and an analgesic response mitigated the negative consequences of deceptive administration. Participants tolerated moderate effectiveness and considerable negative consequences in an acceptable placebo, although results suggest lay individuals may not have a sophisticated conceptualization of placebo effectiveness. Studies altering individuals' understanding of placebo effectiveness and mechanisms are needed to identify additional factors determining placebo acceptability. PERSPECTIVE: This study represents an empirical examination of analgesic placebo acceptability among lay individuals. This article is the first to systematically manipulate deception, treatment outcome, and disease severity to determine how these factors interact to differentially determine placebo acceptability-a highly relevant finding that informs the clinical use of placebo.