Researchers propose new masking framework for psychedelic clinical trials

Researchers from the University of California, San Francisco, UC San Diego, and Stanford University are calling for more rigorous masking protocols in psychedelic clinical trials to ensure scientific accuracy. A perspective published in JAMA Psychiatry highlights that current trials struggle with masking, as participants can often identify whether they received a high dose of a psychedelic like psilocybin due to profound alterations in consciousness.

In high-dose psychedelic trials, correct treatment guessing can exceed 90%, making it difficult to distinguish a drug's actual pharmacological effects from the power of participant expectation. Previous attempts at using active placebos, such as niacin or diphenhydramine, have been largely ineffective because they do not replicate the psychedelic experience. Newer single-agent options like THC or dextromethorphan also carry recognizable pharmacological fingerprints that participants can identify.

To address these failures, the researchers propose the UMBRAA framework, which suggests using multidrug active placebos—carefully designed combinations of approved drugs—to create a more convincing placebo effect. They also recommend limiting the information disclosed to participants about the study to reduce the likelihood of treatment guessing. The authors argue that without these improvements, the true efficacy of these compounds may not be rigorously established as regulators face increasing pressure to evaluate their potential for treating serious mental illness.