The Underappreciated Placebo Effects and Responses in Randomized Controlled Trials on Neck Pain: A Systematic Review With Meta-analysis

Abstract

Objective: To quantify placebo effects and responses in randomized controlled trials (RCTs) on neck pain and explore how they would influence the treatment of neck pain. Data Sources: We searched MEDLINE (PubMed), EMBASE (Ovid), CINAHL (EBSCO), Physiotherapy Evidence Database (PEDro), and World Health Organization International Clinical Trials Registry Platform from the inception of August 15, 2021, to identify relevant RCTs. Study Selection and Data Extraction: The abstracts and full texts of potential studies were independently screened, and data extraction was also independently performed by 2 researchers. Scales of the score measuring neck pain and the scores both at baseline and the endpoint were extracted. Data Synthesis: A total of 60 RCTs were included. The mean improvement in the pain score after placebo treatment was 15.65 (mean difference [MD]=-15.65, 95% confidence interval; CI [-19.19, -12.12]; P