Purpose: To consider the nature of cannabis-related harms under the United Kingdom’s Misuse of Drugs Act (MDA). Written for the specific context of this four-paper special section on 50 years of the MDA, it argues that the MDA may cause more harm than it prevents.

Design/methodology/approach: An opinion piece offering a structured overview of cannabis-related harms under prohibition. It summarises existing evidence of the ways in which prohibition may exacerbate existing – and create new – harms related to the production, distribution, use and control of cannabis.

Findings: The paper argues that prohibition of cannabis under the MDA may cause more harm than it prevents.

Originality: It has long been argued that the MDA does not accurately or fairly reflect the harms of the substances it prohibits, and much existing research points to different ways in which drug prohibition can itself be harmful. The originality of this paper lies in bringing together these arguments and developing a framework for analysing the contribution of prohibition to drug-related harm.