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How to Study Placebo Responses in Motion Sickness with a Rotation Chair Paradigm in Healthy Participants

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Published on: December 14, 2014

A systematic review found no consistent difference in effect between more and less intensive placebo interventions.

Margrit Fässler¹, Karin Meissner¹, Jos Kleijnen²

¹Institute of General Practice, Klinikum rechts der Isar, Technische Universität München, Orleansstrasse 47, 81667 Munich, Germany.

Journal of Clinical Epidemiology

|February 3, 2015

Summary

More intense placebo interventions were not consistently linked to greater clinical effects than less intense ones. This systematic review found no definitive evidence that placebo intensity influences outcomes in randomized clinical trials.

Keywords:

Placebo effect Placebos Randomized controlled trial Systematic review Therapy Treatment outcome

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Area of Science:

Clinical Research
Medical Interventions

Background:

The intensity of placebo interventions may influence their clinical effects.
Evidence from direct comparisons within randomized clinical trials (RCTs) is needed to support this hypothesis.

Purpose of the Study:

To systematically review RCTs with multiple placebo groups.
To investigate if more intense placebo interventions yield larger clinical effects than less intense ones.

Main Methods:

Systematic review of RCTs identified via electronic searches and citation tracking up to February 2013.
Placebo interventions were categorized as more or less intense based on complexity, invasiveness, administration route, and application time.
Included 12 studies with 1,059 patients receiving placebo.

Main Results:

Seven studies found no significant differences between more and less intense placebos.
Four studies reported differences for single outcomes.
One study found significantly larger effects for more intense placebos.
Explorative meta-analysis showed a standardized mean difference of -0.22 (95% CI: -0.46, 0.02; P = 0.07).

Conclusions:

More intense placebo interventions were not consistently associated with larger clinical effects compared to less intense placebos in the reviewed studies.
The hypothesis that placebo intensity directly correlates with effect size is not robustly supported by current direct comparative evidence.