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Karin Meissner
Head of the Placebo Research Group, Institute of Medical Psychology, Ludwig-Maximilians-University Munich & Professor of Integrative Medicine, University of Applied Sciences and Arts Coburg

Differential effectiveness of placebo treatments

The size of placebo effects depends on various contextual factors, including the type and characteristics of the placebo intervention. Several systematic reviews provided evidence that more intense placebo interventions are associated with larger placebo effects than less intense ones. For example, sham acupuncture and sham surgery were associated with significantly higher placebo response rates than oral placebos in 79 randomized placebo-controlled studies of migraine prophylaxis (Meissner et al., JAMA Int Med 2013). Similarly, a review of 149 randomized trials on knee osteoarthritis showed intra-articular and topical placebo interventions to induce larger improvement than oral placebos (Bannuru et al., Ann Intern Med 2015). However, a systematic review of 12 studies allowing a direct comparison of different placebo treatment modalities within the same study did not reveal consistent evidence for greater effectiveness of more intense placebos (Fässler et al., J Clin Epidemiol 2015). Likewise, in an experimental paradigm we recently found no evidence for a differential effectiveness of more and less intensive placebo interventions in the treatment of nausea (Meissner et al., submitted). Thus, while there is accumulating evidence from indirect comparisons of placebo groups in clinical trials that the placebo effect size varies systematically according to type of intervention, evidence from studies allowing a direct comparison still challenges this view. Possibly, not only the type of treatment, but also other closely related contextual factors, such as treatment duration and the amount of attention provided by doctors and nurses, contribute to the observed differences of placebo effectiveness across treatment modalities. Implications of the results for the design and interpretation of clinical trials will be discussed.

Biosketch

Karin Meissner, MD, is Head of the Placebo Research Group at the Institute of Medical Psychology at the Ludwig-Maximilians-University Munich and since 2016 also a full professor of Integrative Medicine at the University of Applied Sciences and Arts in Coburg. Her research interests include meta-analyses of placebo effects in clinical trials, psychobiological correlates of placebo effects in nausea and appetite regulation, and mechanisms of placebo effects on autonomic organ functions. She is also interested in the evaluation of CAM treatments to optimize the care of chronically ill patients. Her research has been funded by the German Ministry for Science and the German Research Foundation (DFG).