Next phase of cannabidiol (CBD) trial for Parkinson’s non-motor symptoms needs participants in the UK

The study builds on the results from the pioneering Parkinson’s UK funded trial launched in 2019.

Around 3 in 4 people with Parkinson’s will be affected by symptoms such as hallucinations and delusions at some point. Hallucinations can mean that the person sees, hears or feels things that aren’t there, or mistakes objects for other things. This can be very distressing for the person and their loved ones.

Symptoms like these are known as Parkinson’s-associated psychosis. Sometimes, they are a side effect of Parkinson’s medication, but they can also be a  direct symptom of the condition. Current treatments for psychosis are not very effective, or come with unwanted side effects.

That’s why, in 2019, Parkinson’s UK announced funding for a pioneering clinical trial alongside King’s College London. The trial aimed to understand whether cannabidiol (CBD), part of the cannabis plant, might be useful for treating symptoms of psychosis in people with Parkinson’s. This study is called the CAN-PDP study.

The first phase of the study aimed to find a suitable dose of manufactured CBD that could be taken by people with Parkinson’s. This involved studying 24 people taking the drug over 6 weeks and monitoring how well the drug was tolerated.

Results from that phase of the study gave researchers an idea of a suitable dose for further testing. The team have now moved to the next phase, to test how well this dose of CBD can reduce symptoms of psychosis.

What happens next?

The next phase of the trial needs to recruit 120 people with Parkinson’s who experience any kind of hallucination, or abnormal beliefs or thoughts which aren't true (delusions). Participants will be asked to take either the CBD drug, or a dummy drug (placebo) for 12 weeks and report on how their symptoms change over this time.

Neither the people taking part or the researchers will know who is taking the CBD or the placebo drug. This is called a double-blind study, the current gold standard for understanding whether a new treatment really works.

How can I take part?

The research team is looking for people with Parkinson’s to take part in the trial. To take part, you must be over the age of 40, and have experienced symptoms of psychosis for at least one month. There are 10 trial sites across England and Wales. Find your nearest trial site and how to get involved on our Take Part Hub.

Barry was involved in the first part of the study. His wife Brenda said:
“The trial gave us hope. We had been waiting for the second stage of the CAN-PDP trial to start. Barry is about to finish stage 2 next week and there has been no problem taking the medication.

"The travel from the South Coast to the research hospital in London was doable but it would have been easier if there had been another centre nearer.

"With it being double-blind we’re not sure if he’s been taking the study drug or the placebo. But we know it’s important to gather all the data to come to a conclusion.

“Drug development cannot happen without people like Barry putting themselves out there and getting involved."

Dr Sagnik Bhattacharyya is one of the researchers leading the study. He said: 
“Supported by Parkinson’s UK, we are pleased to be carrying out the next phase of this groundbreaking study. Your participation is vital to help us answer this question and is necessary to take the next step towards making a better treatment accessible for people with Parkinson’s psychosis.”

Whilst past trials have shown promise, there is still more research needed to show if CBD can be a safe and effective treatment for Parkinson's. This includes safe testing of dosages and frequencies. Parkinson's UK does not recommend you take any medications without a prescription. If you have any questions, please contact our research mailbox at [email protected].