The role of positive information provision in open‐label placebo effects

Abstract

Open label placebos (OLPs) appear generally efficacious among clinical samples, but the empirical evidence regarding their use in non‐clinical and sub‐clinical samples, as well as when administered independent of a convincing rationale, is mixed. Healthy participants (N = 102) were randomised to either a 6‐day course of OLP pills with information provision (OLP‐plus: N = 35), without information provision (OLP‐only: N = 35), or no‐treatment control group (N = 32). OLP pills were described as enhancing physical (symptoms and sleep) and psychological (positive and negative emotional) well‐being. Well‐being was assessed at baseline and on Day 6. Expectancies and adherence were measured. OLP administration interacted with baseline well‐being. The OLP‐plus group demonstrated increased well‐being on all outcomes other than positive emotions, but only when they reported decreased baseline well‐being. OLP‐only and control groups did not differ. The OLP‐plus group demonstrated elevated expectancies, that mediated the OLP effect on physical symptoms relative to control, but only when well‐being was lower than average at baseline (i.e. moderated‐mediation). Results demonstrate the importance of information provided with OLPs. The moderating effect of baseline outcomes may reconcile inconsistent results regarding clinical and non‐clinical samples. Accounting for baseline symptoms in non‐clinical and sub‐clinical samples is likely to enhance our understanding of when OLPs are effective.

Open-label placebos enhance test performance and reduce anxiety in learner drivers: a randomized controlled trial

“…We also found that the more the learner drivers suffered from test anxiety in general, the more they profited from the OLP treatment. This is in line with recent studies 46 , suggesting that OLPs with respect to anxiety are most promising in individuals with high anxiety feelings, and also with the general finding that OLP treatments seem to be stronger in patients than in non-clinical samples 14 , 15 .…”

“…Therefore, it has been suggested that only double blind placebo effects may be based on prefrontal brain areas (which is thought to reflect expectation 20 ), whereas OLP effects may be based on lower control mechanisms 45 . Several OLP studies support this view by demonstrating that expectation did not predict placebo responses ( 23 – 25 but see, e.g., 26 , 46 ). Hence, conventional double-blind placebos and OLPs may be based on different mechanisms 47 .…”

Practitioner warmth and empathy attenuates the nocebo effect and enhances the placebo effect

“…This methodological choice was intentional to avoid participants guessing the true nature of the study. While similar single-item expectancy measures have been associated with placebo and nocebo effects in similar paradigms (e.g., Barnes, Babbage, et al, 2023;El Brihi et al, 2019;Quinn et al, 2023), a more comprehensive measure, such as the Treatment Expectation Questionnaire may provide greater specificity (Jannis et al, 2020).…”

“…Lower scores indicate increased psychological well-being. Responses were sum-scored and then doubled to make them comparable to the full measure, the DASS-42 (as published elsewhere; Barnes, Babbage, et al, 2023).…”