The first on the dark side of the moon: Revisiting the first nonblind placebo trial.

Open-label placebos have been studied extensively and with rigor for about 15 years, and clinically meaningful effects have been replicated in experiments and clinical trials since then, across countries, with different populations, with differing methodologies. But are open-label placebos the first to harness placebo effects in an ethically manner? Not quite. About 60 years ago, Lee C. Park and Lino Covi conducted a study using so-called nonblind placebos in psychiatric patients, with striking effect. But how was this study possible as there were hardly any antecedents as much as there were no discernible subsequents for 45 years, i.e. until 2010. When one of the authors (AFN) received a short email in March 2025, it was to our surprise and joy to find it written by no other that Lee C. Park himself, 60 years to the month after the publication of the "Nonblind placebo trial". Between July and October 2025, a vivid email dialogue emerged on how the idea of using placebos with full disclosure evolved and how it has been received by patients and colleagues at the time, including the discussion of ethical and practical issues. This also included the relationship between psychotherapy and placebos and why the placebo effect also may be better labeled as a brief psychotherapy effect.