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Psilocybin in Depression Resistant to Standard Treatments (PsiDeR) Study

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A third of those with clinical depression cannot find an effective treatment. King’s College London are evaluating the feasibility, safety and effectiveness of psilocybin-assisted therapy for treatment resistant depression.

The PsiDeR Study is funded by the National institute of Health and Care Research. King’s researchers are conducting a clinical trial to evaluate the feasibility, safety and efficacy of psilocybin for adult participants who are unresponsive to, or intolerant of, at least two treatments for depression. Participants either receive a single dose of 25 mg psilocybin or a placebo and all participants receive a package of psychological therapy. The study will assess changes in the level of depression at 3 weeks, and 6 weeks. With further informed consent, this study is collecting neuroimaging and omics data to analyse possible mechanisms behind effects and biomarkers.


This is a phase 2, randomised, placebo-controlled trial investigating psilocybin therapy as a treatment for treatment resistant depression.

All participants enrolled in this trial will be randomised to receive either 25mg of psilocybin or placebo (0mg of psilocybin) alongside talking therapy. There is the choice to take part in an ‘open-label extension’ once completing the trial, where participants will be guaranteed 25mg of psilocybin. There is also a choice to take part in the neuroimaging (brain scan) element of the trial.

Participating in the trial

If you wish to volunteer for this trial, please consider your decision carefully. There are strict inclusion and exclusion criteria the team cannot deviate from. You will be usually asked to attend the research facility on numerous occasions, without much flexibility for variation in dates. Clinical trials are not the same as receiving treatment from your doctor or therapist. We use placebos or variable doses in some of our trials. You may not get the treatment you want and the team is unable to change this, for any reason.

For one reason or another, most people who volunteer turn out not to be eligible for a clinical trial. It’s important to be realistic about the chances of inclusion and pursue other sources of help at the same time.

Effects of Psychedelics

Depending on the drug, psychedelic therapy lasts from about 2 to 8 hours. We only give people psychedelics in a dedicated hospital facility with support from doctors, nurses, psychotherapists and study coordinators. We don’t give people psychedelics to take home.

It isn’t possible to predict how psychedelics will affect an individual person. Clinical trials are an experiment. They are being done because we do not yet know if psychedelic therapy is a safe and effective form of treatment. Therefore, your participation in a trial comes with some risks. Your condition could improve, stay the same or it could worsen.Psychedelic therapy is not a ‘reset’ for your brain and it is not a ’quick fix’. Regardless of what happens, it’s important to have the right support around you if this happens. There are limits to the extent the study team can support you, particularly out of normal office hours.

Trials Design


Ongoing, recruitment closed 



Clinical area

Treatment resistant depression


Psilocybin therapy

Recruitment period




National Institute for Health and Care Research


King’s College London & The South London & Maudsley NHS Foundation Trust

Our Partners


National Institute for Health Research (NIHR)