A clinical trial of 5 mg psilocybin plus psychological support vs 25 mg psilocybin plus psychological support in adults with generalised anxiety disorder
Generalised anxiety disorder (GAD) causes constant, intense worry that can make daily life very difficult. While standard treatments help many people, others still struggle with symptoms. This UK study explores whether psilocybin—an active compound found in magic mushrooms—can provide relief when combined with guided psychological support. Participants will receive two doses of psilocybin, given one month apart, alongside sessions with a trained therapist. The trial compares a low dose (5 mg) with a standard therapeutic dose (25 mg) to learn which works better and how safe they are. The study lasts up to 33 weeks in total. This includes initial health checks, a 7-week treatment period, and 22 weeks of follow-up. A medical doctor and therapist will be present during dosing sessions to provide close care and support throughout your time in the study.
At a glance
What is this study about?
Living with generalised anxiety disorder often means dealing with overwhelming worry, restlessness, and physical tension nearly every day. While medicines like antidepressants and talking therapies are common, they do not work well for everyone. Researchers are looking for new, long-lasting ways to help the brain reset patterns of chronic worry and fear.
This Phase II clinical trial looks at psilocybin, a substance that temporarily alters brain activity and how we perceive thoughts and emotions. When taken in a calm, medically supervised room with therapist guidance, psilocybin may help people work through deep emotional distress and gain new perspectives on their anxiety.
The main goal of this research is to compare a smaller 5 mg dose with a larger 25 mg dose. By comparing the two, scientists hope to understand the best balance between symptom relief and comfort. The findings could pave the way for new, approved mental health treatments across the UK.
Key takeaways
- Tests whether 5 mg or 25 mg of psilocybin combined with therapy works best for generalised anxiety disorder.
- Open to adults aged 18 to 70 with moderate to severe anxiety symptoms.
- Involves two treatment days spaced one month apart in a secure, medically supervised setting.
- The total study commitment lasts up to 33 weeks, including preparation and follow-up checks.
- Taking part is completely voluntary, and you may withdraw at any time.
Who may be eligible?
This trial is open to adults aged 18 to 70 who have a formal diagnosis of generalised anxiety disorder and are currently experiencing moderate to severe symptoms. To take part, you should have a body mass index (BMI) between 18 and 35 and be in generally stable physical health. If you take a standard SSRI antidepressant, you may still join, provided your dose has been steady for at least six months.
You will not be able to participate if you have serious, unstable medical problems affecting your heart, liver, or kidneys. People with epilepsy, a history of seizures, insulin-dependent diabetes, or past brain injuries are also excluded. For safety reasons, the study cannot accept individuals who are pregnant, breastfeeding, or testing positive for recreational drugs or alcohol during clinic visits.
Because the treatment involves discussing deep emotions, doctors will carefully screen out anyone who is currently at high risk of suicide or who has had adverse reactions to psychedelic medicines in the past.
Could this study suit you?
Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.
- I am between 18 and 70 years old.
- I have been diagnosed with generalised anxiety disorder and still feel moderate to severe anxiety.
- My body mass index (BMI) is between 18 and 35.
- I do not have epilepsy, a seizure disorder, or insulin-dependent diabetes.
- I am not pregnant or breastfeeding, and I am willing to use reliable contraception if needed.
- I am willing to attend regular clinic appointments in the UK over roughly eight months.
What does participation involve?
Taking part in the study lasts up to 33 weeks. First, you will complete a screening period lasting up to 4 weeks, where the team checks your medical history, carries out blood tests, and records an electrocardiogram (ECG) to monitor your heart rhythm. Next is a 7-week treatment period. During this time, you will have therapy sessions to prepare, followed by two separate dosing days spaced one month apart. On these days, you will take your assigned psilocybin dose in a private, comfortable room with a doctor and therapist present to support you. After the treatment period, you will enter a 22-week follow-up stage, attending regular check-ins and filling out questionnaires so the team can track your mental health and recovery.
Potential risks and benefits
Locations (1)
- -Approximate-, England
Common questions
Will I know whether I am getting the 5 mg or 25 mg dose?
No. This is a double-blind trial, meaning neither you nor the research staff will know which dose you receive until the study ends. This ensures the results are completely fair and unbiased.
Can I stay on my regular anxiety medication?
You may be able to continue your current SSRI antidepressant if you have been on a stable dose for at least six months. Other psychiatric or herbal medicines may need to be safely stopped before taking part.
What happens during a dosing day?
You will take the capsule in a quiet, comfortable clinic room. A trained therapist and doctor will stay with you throughout the entire session to support you, answer questions, and monitor your physical health.
What support is available if I feel distressed after a session?
You will be given a 24-hour contact telephone number to reach the clinical team at any time if you experience emotional difficulties or medical concerns between visits.
Do I have to pay to take part in this study?
No, you do not pay for the medication, therapy, or medical checks. Clinical trials typically cover study-related medical costs and may help reimburse your travel expenses.
How to find out more
Rebeca James
Always speak to your GP or specialist before deciding to take part in a study.
Interested in taking part?
Discussion
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