The authors conducted a large meta-analysis examining whether the similarity between active treatments and sham control interventions affects trial outcomes, participant blinding, and attrition. They found that differences in treatment exposure, participant experience, and treatment context were associated with variations in reported treatment effects and blinding success. More closely matched sham controls were linked to important differences in trial results, supporting concerns that inadequate blinding may inflate estimates of treatment efficacy. Overall, the review demonstrates that control intervention design is a critical methodological issue in pain research and provides evidence to inform future standards for trial design and reporting.