Factors Influencing Placebo Responses in Rheumatoid Arthritis Clinical Trials: A Meta-Analysis of Randomized, Double-Blind, Placebo-Controlled Studies.

A better understanding of placebo responses and the specific factors influencing these outcomes is important for clinical trial design. We investigated the magnitude of placebo responses at 3 months and the potential factors influencing these outcomes in rheumatoid arthritis (RA) clinical trials.