Screening and Eligibility in Clinical Research

Why trials screen

Researchers' safety guidelines name the most likely risk as overwhelming distress during the drug's effects, which could lead to dangerous behavior, and less commonly prolonged psychosis. The safeguards they list include excluding people with a personal or family history of psychotic disorders or other severe psychiatric disorders. [1] The reasons are about risk and about clean results: the FDA also notes that enrolling people with prior psychedelic exposure can create expectation bias. [2]

What a published trial excluded

A psilocybin trial for major depression (27 adults) excluded people using antidepressant medications, and people with histories of psychotic disorder, serious suicide attempt, or hospitalization. [3]

This is one trial among many. Other trials set different criteria, and we did not read their full protocols. Because these groups were excluded, results may not apply to them. See how to read a psychedelic clinical trial.

What the FDA says

• Heart valves. For medicines that act on the 5-HT2B receptor, the FDA says people with preexisting valvulopathy or pulmonary hypertension should be excluded until cardiac risk is characterized. [2]
• Medicines. The FDA notes that SSRIs, SNRIs or MAOIs used for 3 weeks or more may reduce the subjective effects of psychedelics, while tricyclic antidepressants or lithium may potentiate them, creating a potential psychiatric safety concern. [2] The guidance says more research is needed. It describes trial design, not advice for patients. See serotonergic medicines and interactions and toxicology.
• Not excluding too much. The FDA also advises trials not to unnecessarily exclude groups who would use the treatment after approval. [2]

Common questions about "self-screening"

No validated self-screening tool appeared in the sources we read. Proper evidence not found for a questionnaire or checklist shown to identify who can safely use psychedelics outside supervised care. We checked the FDA guidance, the safety guidelines and the trial above. Risks that screening tries to address are covered in contraindications, psychosis vulnerability and cardiovascular risks.

Related guides

• Informed consent
• Clinical monitoring