Blinding in Placebo-Controlled Trials

The document contains letters discussing the validity and methodology of clinical trials, including a critique of "distant healing" studies and a defense of a study on zinc lozenges for the common cold. One letter argues that there is no substantial evidence supporting the effectiveness of intercessory prayer or "distant healing," attributing any minor effects to the placebo effect. Another letter by Ananda S. Prasad, MD, PhD, defends the methodology of a study on zinc lozenges, asserting that the blinding was adequate despite potential taste differences between the lozenges. Norman A. Desbiens, MD, counters that a regression analysis could have determined if the study's results were confounded by participants guessing their treatment group. The document highlights the necessity of maintaining blinding in clinical trials to ensure the integrity of the study results.