Brain scan study to finally test if low serotonin causes depression
NCT ID NCT07651293
First seen Jun 27, 2026 · Last updated Jun 27, 2026
Summary
This study will test the long-standing theory that depression is caused by low serotonin levels in the brain. Researchers will give a single dose of fenfluramine (a drug that releases serotonin) to 46 people—half with depression and half healthy—and use PET brain scans to measure serotonin release. The goal is to see if people with depression have a weaker serotonin response, which could help explain why some antidepressants work and others don't.
What this could mean
Our plain-language read of the trial. This is informational only — not medical advice or a prediction.
- Active substance
- Fenfluramine hydrochloride (a serotonin-releasing drug)
- What this could lead to
- If successful, this study could clarify whether serotonin deficiency plays a key role in depression and help identify who might benefit from SSRI antidepressants.
- What could go wrong
- This is a small, early-stage observational study (46 people) that does not test a new treatment. Fenfluramine is used only as a probe, not as a therapy. Results may not apply broadly.
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Conditions
The condition(s) this trial relates to.
As listed by the trial registrant
The condition terms exactly as the trial's registrant entered them.
Contacts and locations
Locations
-
entre for Psychedelics Research, Division of Psychiatry Imperial College London, Level 2, Commonwealth Building, Hammersmith Campus, Du Cane Road, London
London, W120NN, United Kingdom
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