A clinical trial backed by the Royal College of Psychiatrists will see up to 20,000 British patients given medical cannabis over the next two years.

The UK government legalized cannabis for medicinal purposes in October 2018, but only a handful of patients have been able to receive it due to stringent NHS guidelines. It is hoped this trial will persuade the NHS to permit medical cannabis prescriptions for a range of conditions.

The project is spearheaded by the British government’s former drug tsar, Professor David Nutt. He published a controversial paper in 2009 declaring that cannabis should be reclassified as it is a lot less harmful than tobacco and alcohol, and the resulting outcry led Home Secretary Alan Johnson to sack him.

Nutt has continued to campaign for a liberalization of Britain’s cannabis laws, and the public perception of cannabis has dramatically improved over the past decade. He now works for independent scientific body Drug Science, which has launched Project Twenty21.

It will see up to 20,000 patients given medical cannabis by 2021 in order to take part in clinical trials. Crucially the project is backed by the Royal College of Psychiatrists, one of the UK’s leading medical bodies, and it will be launched at that RCP headquarters on Thursday.

The current NHS guidelines, which essentially prevent doctors from actually prescribing cannabis to patients, were laid down by the Royal College of Physicians and The British Paediatric Neurology Association. The Royal College of Psychiatrists is a separate body, but it is influential.

“The RCP hopes this project will address the paucity of evidence for the use of cannabis-based medicinal products in all health settings, including mental health,” said Professor Wendy Burn, the RCP president.

Project Twenty21 will study the effect of cannabis on patients suffering from chronic pain, epilepsy, multiple sclerosis, post-traumatic stress disorder, Tourette’s syndrome, anxiety disorder and substance abuse.

Dr. Arun Bhaskar, president of the British Pain Society, has also thrown his weight behind the project. He said there are more than 8 million people with disabling chronic pain in the UK and medical cannabis is still out of reach for them, a situation he hopes this trial changes.