Oxford study to trial cannabis-based medicine as treatment for psychosis

Oxford scientists are to launch a major global trial to investigate whether cannabis-based medicine can treat people with psychosis or psychotic symptoms.

Currently, cannabidiol (CBD) is only prescribed for a small number of conditions. In the UK, for example, these include rare, severe epilepsy, and vomiting or nausea caused by chemotherapy.

The international study will involve 35 centres, mainly in Europe and North America. It will be coordinated by the University of Oxford’s department of psychiatry, which has been awarded £16.5m by the charitable foundation Wellcome.

“Cannabidiol is one of the most promising new treatments for people with psychosis,” said Oxford’s Prof Philip McGuire, who is leading the trial. “Many people with psychosis are open to trying cannabidiol and previous smaller-scale studies have indicated that it has beneficial effects.”

CBD is one of the chemicals found in marijuana but it does not contain tetrahydrocannabinol (THC), the ingredient in marijuana which produces a feeling of intoxication.

The stratification and treatment in early psychosis (Step) programme will involve 1,000 people, including those at clinically high risk of psychosis, people with a first episode of psychosis and patients with psychosis who have not responded to conventional treatment.

Jazz Pharmaceuticals has supplied the CBD for the study at no cost. “As well as treating psychosis that is already established, the study will also investigate whether cannabidiol can prevent the onset of psychosis in people at high risk of developing it,” said McGuire. “This study could provide us with a new kind of treatment for psychosis and we are hugely grateful to Wellcome and Jazz Pharmaceuticals for helping to make it happen.”

The form of cannabidiol that is being used in the study is Epidyolex, which is approved for some children and adults with epilepsy.

Lynsey Bilsland, the head of mental health translation at Wellcome, said: “This exciting programme will help us to find out if cannabidiol is effective at treating psychosis at various stages by testing it at scale.

“While antipsychotics are commonly used to treat psychosis, they can have significant side effects, patients often stop taking them, and they don’t work for everyone. This means that it is important that we explore avenues such as this one for new therapies.

“In addition, as part of these trials the researchers are aiming to identify biomarkers – biological signposts – which would indicate that a patient might respond well to the treatment. This will allow for greater personalisation of treatment in the future.”