# Placebo and Nocebo Effects in Motor Performance: An Overview of Reviews

## TL;DR

This umbrella review finds that placebo and nocebo effects on motor performance vary widely, but the evidence is often of poor quality.

## Contribution

The study provides a comprehensive assessment of the methodological quality and effect sizes of existing reviews on placebo and nocebo effects in motor performance.

## Key findings

- Placebo and nocebo effects on motor performance ranged from small to large in magnitude.
- Most reviews had poor methodological quality and limited use of GRADE assessments.
- Only a few reviews included meta-analyses with substantial participant numbers.

## Abstract

To assess and synthesize the effect size and quality of the literature on the placebo and nocebo effects on motor performance and motor‐related perceptive responses.

Umbrella review.

Medline, Embase, Lilacs, Cochrane Database of Systematic Reviews for peer‐reviewed literature, PROSPERO for protocols, and the Open Access Theses and Dissertations for gray literature.

Population—human participants with varied health conditions; intervention: placebo; control: no treatment or active intervention; outcome: motor performance (primary) and perceptual variables (secondary); study design—ystematic reviews with or without meta‐analysis.

In total, 3432 records were gathered from searches, resulting in 13 eligible reviews after screening. These reviews encompassed 247 original studies, with 221 focusing on the placebo effect and 26 on the nocebo effect. Among all eligible systematic reviews, five conducted meta‐analysis with 5036 participants, and one provided a summary of effect sizes reported by the original studies with 1215 participants. The reviews reported small to large effects of placebo (SMD = 0.09–0.93) and nocebo (SMD = 0.37–1.20), and only two conducted the GRADE assessment.

We found varied placebo and nocebo effects on motor performance, likely due to the poor quality of the methodology used by most reviews, highlighting the need for well‐conducted systematic reviews on the placebo and nocebo phenomena.

This umbrella review assesses the methodological quality and certainty of evidence in systematic reviews on placebo and nocebo effects in motor performance. The findings reveal significant variability in effect sizes, ranging from small to large, and highlight concerns regarding the quality and bias in the existing literature.