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

PLoS ONE, vol. 16, pp. e0247103

Abstract

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.

Authors 9

1. Rosanne M. Smits corresponding Aachen Health Medical and Neuropsychology Unit Leiden Institute for Brain and Cognition

   Leiden University · Wilhelmina Children's Hospital

   Affiliation as printed

   Health, Medical and Neuropsychology unit, Leiden University, Leiden, The Netherlands

   Leiden Institute for Brain and Cognition, Leiden, The Netherlands

   Pediatric Immunology and Rheumatology, Wilhelmina Children's Hospital, Utrecht, The Netherlands

   Pediatric Immunology and Rheumatology, Wilhelmina Children’s Hospital, Utrecht, The Netherlands

2. Dieuwke Swaantje Veldhuijzen Aachen Health Medical and Neuropsychology Unit Leiden Institute for Brain and Cognition

   Leiden University · Wilhelmina Children's Hospital

   Affiliation as printed

   Health, Medical and Neuropsychology unit, Leiden University, Leiden, The Netherlands

   Leiden Institute for Brain and Cognition, Leiden, The Netherlands

   Pediatric Immunology and Rheumatology, Wilhelmina Children's Hospital, Utrecht, The Netherlands

   Pediatric Immunology and Rheumatology, Wilhelmina Children’s Hospital, Utrecht, The Netherlands

3. Tim olde Hartman

   Radboud University Medical Center · Radboud Institute for Health Sciences

   Affiliation as printed

   Department of Primary and Community Care, Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, The Netherlands

4. Kaya J. Peerdeman Aachen Health Medical and Neuropsychology Unit Leiden Institute for Brain and Cognition

   Leiden University

   Affiliation as printed

   Health, Medical and Neuropsychology unit, Leiden University, Leiden, The Netherlands

   Leiden Institute for Brain and Cognition, Leiden, The Netherlands

5. Liesbeth Mirjam van Vliet Aachen Health Medical and Neuropsychology Unit Leiden Institute for Brain and Cognition

   Leiden University

   Affiliation as printed

   Health, Medical and Neuropsychology unit, Leiden University, Leiden, The Netherlands

   Leiden Institute for Brain and Cognition, Leiden, The Netherlands

6. Henriët van Middendorp Aachen Health Medical and Neuropsychology Unit Leiden Institute for Brain and Cognition

   Leiden University

   Affiliation as printed

   Health, Medical and Neuropsychology unit, Leiden University, Leiden, The Netherlands

   Leiden Institute for Brain and Cognition, Leiden, The Netherlands

7. Ralph C. A. Rippe Aachen Research Methods and Statistics Institute of Education and Child Studies

   Leiden University

   Affiliation as printed

   Research Methods and Statistics, Institute of Education and Child Studies, Leiden University, Leiden, The Netherlands

8. Nico Wulffraat

   Wilhelmina Children's Hospital

   Affiliation as printed

   Pediatric Immunology and Rheumatology, Wilhelmina Children's Hospital, Utrecht, The Netherlands

   Pediatric Immunology and Rheumatology, Wilhelmina Children’s Hospital, Utrecht, The Netherlands

9. Andrea W.M. Evers Aachen Department of Psychiatry, Leiden University Medical Center Health Medical and Neuropsychology Unit Leiden Institute for Brain and Cognition

   Leiden University · Leiden University Medical Center

   Affiliation as printed

   Department of Psychiatry, Leiden University Medical Center, Leiden, The Netherlands

   Health, Medical and Neuropsychology unit, Leiden University, Leiden, The Netherlands

   Leiden Institute for Brain and Cognition, Leiden, The Netherlands