This preregistered (CRD42021223379) systematic review and meta-analysis aimed to characterize the placebo and nocebo responses in placebo-controlled randomized clinical trials (RCTs) on painful diabetic neuropathy (PDN), updating the previous literature by a decade. Four databases were searched for PDN trials published in the past 20 years, testing oral medications, adopting a parallel-group design. Magnitude of placebo or nocebo responses, Cochrane risk of bias, heterogeneity, and …