People who use cannabis are more likely both to carry out violent acts and to experience violence, according to one of the most comprehensive reviews of the evidence to date, led by researchers at King’s College London.
The team from the Institute of Psychiatry, Psychology & Neuroscience (IoPPN) pooled results from 63 studies involving more than 265,000 people, looking separately at the general population and at people receiving psychiatric care. The review used the World Health Organization’s broad definition of violence, covering physical, sexual and psychological violence towards another person, both within relationships and outside them. The researchers looked separately at violence people reported themselves and violence that led to a criminal conviction, and where a study measured more than one kind of violence, they used the most serious. The findings are published in Psychological Medicine.
Dr Marta Di Forti Co-author of the study from the Institute of Psychiatry, Psychology & Neuroscience (IoPPN) at King's College London, and South London and Maudsley NHS Foundation Trust"As a clinician, I've seen how heavy cannabis use can be a factor in violence. We've been cautious for a long time about how far we could go in describing this link, but a review of this size lets us speak with more confidence about the risks, while being careful not to stigmatise people who use cannabis more broadly."
People who used cannabis were also around one and a half times as likely to be victims of violence. The link was stronger for women than for men.
Professor Sir Robin Murray, senior author of the study from the Institute of Psychiatry, Psychology & Neuroscience at King’s College London, said:
“In the general population, people who used cannabis were around twice as likely to have committed a violent act as those who didn’t; for those in psychiatric care, cannabis users were around two and a half times as likely to be violent as other psychiatric patients who didn’t use cannabis. The link held in studies that followed people over time, though it was smaller than in studies that looked at a single point in time. For violence that led to a criminal conviction, people who used cannabis were three to four times as likely to have been convicted.
Professor Sir Robin Murray Senior author of the study from the Institute of Psychiatry, Psychology & Neuroscience at King's College London"As cannabis becomes more commercialised and legalised around the world, the conversation about its risks has focused mostly on the person using it. This review shows that violence, both committing it and experiencing it, needs to be part of that conversation too."
The researchers say the findings support routinely asking about cannabis use when assessing the risk of violence in mental health services, and including risk of violence in public health messaging about cannabis.
The researchers note that the review shows an association, and cannot prove that cannabis causes violence, as cannabis use often goes alongside other factors that may also raise the risk, such as other drug and alcohol use and difficult social circumstances. Few of the studies measured how much or how often people used cannabis, and the findings on convictions come from a small number of studies. Most were also carried out before high potency cannabis became widespread, and the researchers suggest that daily use of today’s more potent types may show greater effects.
The study was supported by the National Institute for Health and Care Research (NIHR) Biomedical Research Centre: Maudsley and the Medical Research Council.
Links
- Trotta G, Rodriguez V, Marino P, et al. Cannabis use is associated with increased risk of violence: a systematic review and meta-analysis. Psychological Medicine. 2026;56:e296. DOI: 10.1017/S0033291726105856
- The Telegraph, Cannabis users ‘twice as likely to be violent’
