Finding and Understanding Registered Clinical Trials

A registry record is a plan, not a finding

When a company or university tests a drug in people, it is expected to describe the study in a public trial registry. The record says what the study intends to do: who can join, what is compared, and what will be measured. It is not a report of what was found. The World Health Organization (WHO) calls registering all interventional trials a scientific, ethical and moral responsibility. [1]

This page shows how to read such a record for psychedelic and related research. It does not tell you how to join a trial or take any substance; see investigational research and clinical trial access for the access questions.

Evidence labels: insufficient evidence (no usable results yet) and marketing claim (a statement used to attract attention or clients, not shown by the sources read). A registered trial without results earns neither a benefit label nor an approval label.

Where to look

• ClinicalTrials.gov is a large registry of studies. We read its public data interface on 2026-10-22.
• WHO ICTRP is a search portal, not a registry. WHO says it cannot register a trial and that registration goes through its primary registries. [1] The portal can be reached at trialsearch.who.int. [1]
• Other countries run their own registries, which we did not read for this page.

The Research Library's evidence search is the place on this site to look for published studies, which is a different step from checking a registry.

Reading one record: a worked example

The record below is an example of the layout only. It is not an endorsement, and it is not a result. Record NCT05947383 describes itself as a Phase 2, randomized, double-blind, placebo-controlled study of up to two doses of psilocybin for major depressive disorder in adults with cancer. [2]

Study status on ClinicalTrials.gov can be one of a fixed list, including withdrawn, terminated, completed and unknown. [4] The record itself should explain any status other than recruiting or completed.

How big is the field

On 2026-10-22, a search of ClinicalTrials.gov for psilocybin as an intervention returned 307 records, of which 23 had results posted on the registry. [5] This is a count of records matching a search term, not a count of distinct trials or successes. It includes trials of all sizes, designs and conditions.

Why a registered trial is not evidence of benefit

• No result yet. Many records describe studies still enrolling or not yet reported.
• Results are not always posted. A 2026 analysis of 336 MDMA and psilocybin trials registered by March 2025 found 72.0% of completed trials had not reported results on ClinicalTrials.gov. [6]
• Plans change. The same analysis found major changes to the primary outcome measure in 17.6% of trials and to eligibility criteria in 28.6%, mostly after recruitment began. [6] Check the record's change history against the published paper.
• Safety data can differ between sources. Only three of 29 trials with both posted results and a publication showed full agreement in adverse event reporting. [6]
• Therapy and drug are mixed. FDA notes that the contribution of the psychotherapy part to any benefit has not been characterized. [3]
• Follow-up matters. FDA recommends following participants beyond 12 weeks and suggests blinded long-term follow-up, typically 12 months. [3]

A short checklist

1. Search by substance and condition, then open the full record, not the list entry.
2. Note the design: randomized? Compared with what? How many people?
3. Read the primary outcome and the time frame, and check whether they match the published paper.
4. Check the status and the last update date.
5. Look for posted results or a linked publication, and compare them with the original plan.
6. Treat news about a "promising trial" as a claim until you have seen the paper. See how to read a psychedelic clinical trial and findings and limits of psychedelic trials.

Clinics that cite "ongoing trials" to support a service are making a marketing claim; see evaluating clinic claims.