Study Goal:

Parkinson’s disease psychosis (PDP) refers to the range of illusions, hallucinations and delusions that people with Parkinson's may experience. The longer someone has had Parkinson’s for, the more likely they are to experience these symptoms. Although there are some options available for treating PDP, they are either not very effective or safe.

The purpose of this study is to test whether a new medicine called Cannabidiol (CBD) is safe and well tolerated in people with Parkinson's Psychosis. It will also see if CBD has any potential to improve the PDP symptoms. CBD is part of the cannabis plant that does not cause psychosis.

What's Involved:

Study participants either take CBD or a placebo (a "fake" sugar pill that looks identical but contains no drug) for 12 weeks. CBD or the placebo is swallowed in capsule form once a day. Participants will be asked to complete medical examinations, clinical assessments and blood tests. Most visits can be completed either at the hospital or at the participant's home. There is also an optional add on study which would involve having brain scans.

Who Can Take Part? 

People who are:

• Aged 40 years or older

• Experiencing symptoms of psychosis after onset of Parkinson’s

• On a stable dose of Parkinson’s medications and psychosis medications (except clozapine)

• Have a reliable informant/caregiver