The Royal College of Psychiatrists is to review its opposition to the legalisation of cannabis.

The organisation has been wary of moves to decriminalise the drug because of concerns of possible negative effects on users’ health.

There is also an association between psychotic illnesses and high-strength varieties of the drug.

But it is now reconsidering its stance due to arguments that legalising cannabis would give the government the power to both regulate its strength and generate tax from its sale.

Over the summer, there was also a wave of pressure on the Government to relax the laws on cannabis to permit its use for medical treatment, particularly the use of cannabis oil to treat epilepsy.

The college is setting up a panel to review current evidence from countries where the drug is already legal.

Dr Adrian James, Royal College of Psychiatrists registrar and panel chairman, told the Daily Telegraph it would start with an “open mind” and review the available research.

He said he remained concerned about the potential risks, but said he recognised the arguments that decriminalisation could prevent users becoming caught up in the criminal justice system.

He said: “As a forensic psychiatrist, the strongest argument is decriminalising behaviour.”

He added: “Our official view is that we are concerned about the health risks and we are against legalisation…on that basis, but there may be arguments that outweigh the psychiatric argument.”

Billy Caldwell, who has a rare form of epilepsy, with his mother Charlotte
Billy Caldwell, who has a rare form of epilepsy, with his mother Charlotte (Brian Lawless/PA)

The college is only reviewing its opposition to decriminalisation at this stage, and may ultimately decide not to change its position.

It will also review medical cannabis, which it supports as a therapy for certain conditions if it has been properly reviewed and approved by the National Institute of Health and Care Excellence.

In June, a six-month supply of cannabis oil was seized from Charlotte Caldwell, whose 12-year-old son Billy has acute epilepsy, as she arrived at Heathrow Airport from Canada.

The product was later returned to the family following an outpouring of support from politicians and the public.

Several other families came forward with their own stories of how cannabis oil had helped to control their children’s seizures.

Conservative MP Crispin Blunt – who co-chairs an all-parliamentary group on drug policy reform – described the UK’s approach as “frankly absurd” considering opiates are freely supplied for medicinal use.

To date, more than 40 countries, including Italy, Finland, Australia, Canada, Switzerland, Germany and the US, have voted to decriminalise cannabis in some form – often for medical purposes such as pain relief.

Cannabis is one of the most commonly used drugs in the UK, with 6.6% of adults – or 2.2 million people – having taken it.