A clinical trial of 5 mg psilocybin plus psychological support vs 25 mg psilocybin plus psychological support in adults with generalised anxiety disorder

This Phase IIb randomised, double-blind trial (n=96) will compare the efficacy and safety of 5 mg psilocybin plus psychological support versus 25 mg psilocybin plus psychological support in adults with severe generalised anxiety disorder (GAD). Participants will receive two doses, one month apart, and their symptoms will be assessed over a total study duration of 33 weeks.

The trial is being conducted at Clerkenwell Health in the UK and is funded by Psychennex Pty Ltd. It aims to determine whether higher doses of psilocybin (25mg) provide greater symptom reduction than lower doses (5mg) when combined with psychological support. Participants, aged 18-70, may or may not be taking selective serotonin reuptake inhibitors (SSRIs).

The primary outcome will be the change in anxiety symptoms measured using the Hamilton Anxiety Rating Scale (HAM-A) at week 8. Secondary outcomes include changes in depression, workplace productivity, healthcare use, and emotional breakthrough during the psychedelic experience. Safety assessments will track adverse effects such as nausea, increased heart rate, and psychological distress. All sessions will take place in a controlled setting with medical supervision.

Trial Details

Background and study aims The aim of this study is to compare the effectiveness and safety of 5 mg psilocybin plus psychological support with 25 mg psilocybin with psychological support in adults with a diagnosis of generalised anxiety disorder (GAD) who may or may not be taking selective serotonin reuptake inhibitors (SSRIs). Who can participate? Patients aged 18 - 70 years with GAD who are still experiencing moderate to severe symptoms What does the study involve? Participants will receive two separate doses of either 5 mg of psilocybin or 25 mg of psilocybin, 1 month apart in combination with psychological support. GAD symptoms are measured at week 8. Participants will take part in a screening period of up to 4 weeks, a treatment period of 7 weeks and a follow-up period of 22 weeks. In total, participants will take part for up to 33 weeks.

Trial Number ISRCTN14487299

Data attribution

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