Negative clinical trials in psychedelic research: Lessons learned and future recommendations

The so-called "psychedelic renaissance" has been largely defined by a narrative of breakthrough successes and transformative clinical potential. However, as the field matures and enters larger, more rigorous Phase II and III trials, researchers are increasingly encountering "negative" results—including failed primary endpoints, non-significant differences from active placebos, and unexpected adverse events. To ensure the scientific integrity and long-term viability of psychedelic medicine, it is critical to move beyond the publication bias that often favors "positive" outcomes.

This symposium explores the lessons learned from unsuccessful or ambiguous clinical trials in psychedelic research, including ketamine for acute suicidality (KETA), psilocybin for treatment-resistant depression (EPIsoDE), and repeated low-doses of LSD for ADHD. We will examine the methodological hurdles that complicate these studies, such as the "expectancy effect," the challenges of blinding, and the impact of varied psychological support frameworks.

We aim to be optimistic in this symposium and will address these "failures" not as an admission of defeat, but more as a necessary step toward robust evidence-based practice. Ultimately, this symposium will provide a transparent dialogue on how negative data can refine therapeutic protocols, improve patient selection, inform future clinical trials, and guide the next generation of psychedelic drug development.