An open-label study is one in which participants and researchers both know who is receiving what. Often there is only one group, so there is no placebo comparison at all. Open-label designs are common early on, when the first question is whether a treatment is safe and practical to give.
Several psilocybin studies are open-label. A 2025 Danish study of 10 adults with alcohol use disorder reported a large fall in heavy drinking days over 12 weeks, and its authors called for randomized placebo-controlled trials (Jensen et al., 2025). A 2026 study of 22 people with PTSD was a nonrandomized open-label trial focused on safety (McGowan et al., 2026).
Open-label results tend to look better than controlled ones. Without a comparison group, improvement could come from time, attention, other treatments or expectancy. Some controlled trials add an open-label phase afterwards, when everyone is offered the drug, so later results there have no placebo comparison (Erritzoe et al., 2026). A 403-person ketamine trial compared with electroconvulsive therapy was also open-label (Anand et al., 2023).
Sources
- Jensen et al., Journal of Psychopharmacology, 2025
- McGowan et al., Journal of Psychopharmacology, 2026
- Erritzoe et al., Nature Medicine, 2026
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