Explaining placebo effects in an online survey study: Does ‘Pavlov’ ring a bell?

Objectives Despite the increasing knowledge about placebo effects and their beneficial impact on treatment outcomes, strategies that explicitly employ these mechanisms remain scarce. To benefit from placebo effects, it is important to gain better understanding in how individuals want to be informed about placebo effects (for example about the underlying mechanisms that steer placebo effects). The main aim of this study was to investigate placebo information strategies in a general population sample by assessing current placebo knowledge, preferences for different placebo explanations (built around well-known mechanisms involved in placebo effects), and attitudes and acceptability towards the use of placebo effects in treatment. Design Online survey. Setting Leiden, The Netherlands. Participants 444 participants (377 completers), aged 16–78 years. Main outcome measures Current placebo knowledge, placebo explanation preferences, and placebo attitudes and acceptability. Results Participants scored high on current placebo knowledge (correct answers: M = 81.15%, SD = 12.75). Comparisons of 8 different placebo explanations revealed that participants preferred explanations based on brain mechanisms and positive expectations more than all other explanations (F(7, 368) = 3.618, p = .001). Furthermore, attitudes and acceptability for placebos in treatment varied for the type of the condition (i.e. more acceptant for psychological complaints) and participants indicated that physicians do not always have to be honest while making use of placebo effects for therapeutic benefit. Conclusion Our results brought forth new evidence in placebo information strategies, and indicated that explanations based on brain mechanisms and positive expectations were most preferred. These results can be insightful to construct placebo information strategies for both clinical context and research practices.