Intended for healthcare professionals

Feature Essay

The case for medical cannabis—an essay by M P Barnes

BMJ 2018; 362 doi: (Published 25 July 2018) Cite this as: BMJ 2018;362:k3230
  1. M P Barnes, honorary professor of neurological rehabilitation
  1. Newcastle University, UK
  1. m.p.barnes{at}

Legal restrictions on the grounds that cannabis has no therapeutic use have impeded research, says M P Barnes, but evidence shows cannabinoids may have benefit in several indications, calling for doctors to be allowed to prescribe the drug as they can in many other countries

Key messages

  • Cannabis has many medicinal properties, which are increasingly recognised worldwide

  • It seems a relatively safe product, with a good risk:benefit profile

  • We need much more research to understand the merits of different strains, different THC to CBD ratios, different modes of ingestion and dosages

  • Such research, however, would be facilitated by legalisation for medical use, and the UK should follow over 40 other countries that have done this.

Cannabis has been used as a medicine for thousands of years. The earliest recorded use dates back to 4000 BC in China. It was recognised as a medicine in both ancient Egypt and India and in the Greek and Roman cultures. In the 19th and 20th centuries it was widely used around the world as a treatment for migraine, neuropathic and musculoskeletal pain, and in childbirth.

In the UK, cannabis was made illegal in 1928 but doctors could prescribe it up to the introduction of the Misuse of Drugs Act in 1971. Cannabis is currently a Schedule 1 drug under the UK Misuse of Drugs Regulations 2001, which means that cannabis is deemed to have no legitimate use or medicinal value. It also remains a Schedule IV drug under the United Nations Single Convention on Narcotic Drugs treaty of 1961—along with heroin—for substances “particularly liable to abuse and to produce ill effects” which is “not offset by substantial therapeutic advantages.”

The illegal status of cannabis has impeded modern research. This is changing in many international jurisdictions, enabling both research into, and the use of, cannabis as …

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