Pioneering clinical trial to treat psychosis in Parkinson’s patients using cannabidiol

A pioneering clinical trial will investigate the use of cannabidiol (CBD) - a compound found in the cannabis plant - in people with Parkinson’s-related psychosis.

Parkinson’s UK, the largest charitable funder of Parkinson's research in Europe, is partnering with scientists at King’s College London and investing £1.2 million in the phase II clinical trial.

This is the first large-scale trial which will aim to provide preliminary evidence for the safety and efficacy of CBD to alleviate the symptoms of Parkinson's-related psychosis, characterised by hallucinations and delusions.

The three-and-a-half-year project is part of the Parkinson’s Virtual Biotech, led by Parkinson’s UK, which is plugging the funding gap in drug development and fast-tracking the projects with the greatest scientific potential, to transform the lives of people with Parkinson’s. Unlike traditional biotech companies, patient priorities and involvement are the primary drivers of the Parkinson’s Virtual Biotech.

There are currently 145,000 people living with Parkinson’s in the UK and between 50 and 60 per cent of them will be affected by psychosis at some point in their life. Hallucinations occur when individuals see, hear or feel things that are not really there. Delusions involve developing fixed beliefs that are not true. These symptoms can be frightening and distressing for people with Parkinson’s and their families and are typically managed with the removal of medication used to treat Parkinson's. If the symptoms persist, antipsychotic drugs are sometimes used, however this can result in worsened motor symptoms and side effects. In the UK, there are no medications licenced for Parkinson's-related psychosis.

In a recent survey, people with Parkinson’s told the charity they would continue to use, or start using, cannabis-derived products if robust evidence became available that they are safe and effective in treating Parkinson's symptoms.¹

The study, due to start recruitment early next year, will begin with a six-week pilot to assess the safety, tolerability and effectiveness of pharmaceutical-grade CBD in people with Parkinson’s-related psychosis. To find the optimum dose, CBD will be delivered orally in capsules at a dose of up to 1,000 mg/day. In the second stage, 120 people with Parkinson’s-related psychosis will be recruited to take part in a 12-week double-blind, placebo-controlled study.

Scientists will assess the safety and effectiveness of CBD, with half the group receiving the compound and half a placebo. Researchers will then carry out detailed assessments of psychotic, motor and non-motor symptoms. Brain imaging will be used to investigate the effects of CBD.

The announcement comes ahead of final guidance on medicinal cannabis which is due to be published by The National Institute for Health and Care Excellence next month.

Dr Arthur Roach, Director of Research at Parkinson’s UK, said:

“We know from a recent survey we carried out, that people with Parkinson's would continue to use, or start using, cannabis-derived products if robust evidence became available that they are safe and effective in treating Parkinson's symptoms. One of the key questions this clinical trial will address is if CBD is safe to use for Parkinson’s-related psychosis, which has never been done before.

“This trial will provide evidence of the value of CBD to treat the symptoms of hallucinations and delusions in people with Parkinson’s. This could result in a regulated cannabinoid-based medicine being prescribed and used in the clinic, as opposed to self-administration of expensive supplements that have not been monitored for their composition or effects.”

“The projects funded through the Parkinson’s Virtual Biotech are driven completely by the Parkinson’s community. We hope this unique trial will demonstrate the potential of CBD to alleviate some important symptoms and bring us one step closer to delivering a treatment that will improve the quality of life for those affected.”

Lead Researcher, Professor Sagnik Bhattacharya, Professor of Translational Neuroscience and Psychiatry at King’s College London, said:

“Through funding from the Parkinson’s Virtual Biotech this clinical trial will determine, for the first time, whether CBD can correct the abnormal functioning of the brain that is causing symptoms such as hallucinations and delusions. Current treatments prescribed by clinicians for psychosis typically work by blocking dopamine receptors which can increase the problems people with Parkinson’s experience with movement and other symptoms of the condition.

“We will be assessing how safe CBD is for people with Parkinson’s, what the correct dosage is and how it is tolerated alongside the different medications someone with the condition may already be on. The study will also look at the effect of CBD on other symptoms which will pave the way for scientists to investigate the potential of the compound in treating these in future studies. We hope that this will progress to large-scale clinical trials – the final step towards becoming a new treatment that will improve the lives of people with Parkinson’s.”


For more information on the Parkinson’s Virtual Biotech, the symptoms of Parkinson’s and tips on managing Parkinson’s-related psychosis, visit

Media enquiries

For further information/case studies/interview requests please contact:

Parkinson’s UK:

Anita Salhotra, Senior Media and PR Officer on 020 7932 1361 or email / Amy Dodge, Media and PR Manager, on 020 7932 1362 or email

King’s College London:

Robin Bisson, Senior Press Officer, Institute of Psychiatry, Psychology & Neuroscience / +44 20 7848 5377 / +44 7718 697176.

Out of hours please call 07961 460 248 or email

Notes to editors

¹ About the survey ‘Cannabis and Parkinson’s: the views of people with Parkinson’s and health and care professionals’

Between January and March 2019, Parkinson’s UK asked 1,600 people with Parkinson's and 29 health and care professionals to tell them about their experiences with, and opinions on, using cannabis-based products.

The key findings were as follows:

How many people with Parkinson's use cannabis?

  • 59% hadn't used cannabis-derived products before, but would consider using them to control their symptoms

  • 26% had used cannabis-derived products (16% are currently using them for their Parkinson's and 10% have used them in the past)

  • 16% hadn't used cannabis-derived products and aren't interested in using them in the future

  • Overwhelmingly, people with Parkinson's would continue to use, or start using, cannabis-derived products if robust evidence became available that they're safe and effective in treating Parkinson's symptoms

To read the full cannabis and Parkinson's survey findings, visit

Case study

Paula Scurfield (71), from Beckenham, London, was diagnosed with Parkinson’s in 2014 after developing a very slight tremor on one side of her body. To treat the symptoms of slowness of movement, stiffness and rigidity in muscles and fatigue, she was given the drug Levodopa. As a result she developed dyskinesia which is a common side effect. To treat this, she took the drug Amantadine which caused hallucinations at the periphery of her vision. She said it took a lot of trial and error to get a combination of medication that helped with her symptoms.

“Unfortunately the drug which was added to my regime to treat dyskinesia gave me hallucinations – I would see animals running past me in the periphery of my vision every day. At the beginning I thought I was imagining it but then I realised it was a phenomenon. I knew it wasn’t real but it was the most bizarre feeling and I felt a bit scared. My doctor cut the dose in half, which stopped the hallucinations for now.

“The clinical trial is very exciting and if it provides evidence for the safety and effectiveness of CBD, it could benefit those affected by Parkinson's-related psychosis.”

About Parkinson’s UK

Anyone can get Parkinson’s, young or old. Every hour, two more people are diagnosed.

Parkinson’s is what happens when the brain cells that make dopamine start to die. There are over 40 symptoms, from tremor and pain to anxiety. Some are treatable, but the drugs can have serious side effects. It gets worse over time and there’s no cure. Yet.

But we know we’re close to major breakthroughs. By funding the right research into the most promising treatments, we get closer to a cure every day.

Until then, we're here for everyone affected by Parkinson’s. Fighting for fair treatment and better services. Making everyone see its real impact.

We are Parkinson's UK. Powered by people. Funded by you. Together we'll find a cure.

Advice, information and support, is available via our website,, or our free, confidential helpline on 0808 800 0303.

About the Parkinson’s Virtual Biotech

People with Parkinson’s urgently need new treatments. But right now, there’s a huge gap in drug development. The Parkinson’s Virtual Biotech exists to plug that critical funding shortage.

It takes the most promising research and partners with institutions and pharmaceutical companies worldwide to develop the findings into plausible drug treatments. Currently there are projects at the discovery, preclinical and early clinical development stages.

With no large teams of scientists or expensive labs to run, the Parkinson’s Virtual Biotech ensures that every penny of the annual £4m investment goes on what matters most: fast tracking the projects with the greatest potential to transform the lives of people with Parkinson’s.

No one else is doing this. It’s a bold risk. But we believe it will deliver a groundbreaking new treatment by 2024. Because people with Parkinson’s won’t wait. Together, we’ll find a cure.

To find out more, visit

About King's College London and the Institute of Psychiatry, Psychology & Neuroscience

King's College London is one of the top 25 universities in the world (2017/18 QS World University Rankings) and among the oldest in England. King's has more than 26,500 students (of whom nearly 10,400 are graduate students) from some 150 countries worldwide, and nearly 6,900 staff. The university is in the second phase of a £1 billion redevelopment programme which is transforming its estate.

The Institute of Psychiatry, Psychology & Neuroscience (IoPPN) at King's College London is the premier centre for mental health and related neurosciences research in Europe. It produces more highly cited publications in psychiatry and mental health than any other university in the world (Scopus, 2016), with 21 of the most highly cited scientists in this field. World-leading research from the IoPPN has made, and continues to make, an impact on how we understand, prevent and treat mental illness and other conditions that affect the brain.