Placebo effects are among the greatest paradoxes in medical research. Although more data on placebos are available from placebo-controlled trials than on any treatment in medicine, there has been comparatively little deep interrogation of issues related to their measurement, appraisal, and interpretation. Most of the work that has been done, including that in psychiatry, is narrowly focused on...
Importance: Psychedelic drugs possess acute psychoactive effects that can compromise blinding integrity in randomized clinical trials (RCTs). Functional unblinding, when participants or raters correctly identify treatment allocation based on subjective effects, may bias outcomes through expectancy effects, challenging the validity of efficacy estimates and regulatory acceptance. Objective: To...
Abstract Background Psychedelic-assisted psychotherapy has shown potential for psychiatric disorders. However, the magnitude of symptom change in control groups remains poorly understood. We aim to evaluate within-group effects in control groups and compare them to treatment groups in psychedelic trials. Methods A systematic search was conducted up to 1 July 2025. The study protocol was...