Plate Nº 31 · recorded September 29, 2026
Health & Medicine ResearchReported finding
Major Review Links Cannabis Use to Higher Violence Risk
A King's College London review of 63 studies and 265,000 people finds cannabis users roughly twice as likely to commit violent acts — though the link is an association, not proof of cause.
By Marcus Bennett3 min read656 words
In brief
- Researchers pooled 63 studies covering more than 265,000 people, analyzing the general population and psychiatric patients separately.
- Cannabis users were about twice as likely to commit violence in the general population and 2.5 times as likely among psychiatric patients; they were also 1.5 times as likely to be victims.
- The review shows an association only — it cannot prove causation, and most studies predate high-potency cannabis.
People who use cannabis face a higher likelihood of both committing violent acts and becoming victims of violence, according to one of the most comprehensive reviews of the evidence to date. Researchers at King's College London led the analysis, published in the journal Psychological Medicine.
The team, based at the Institute of Psychiatry, Psychology & Neuroscience (IoPPN), pooled results from 63 studies involving more than 265,000 people. They examined two groups separately: the general population and people receiving psychiatric care. The review applied the World Health Organization's broad definition of violence, which covers physical, sexual and psychological violence toward another person, both inside relationships and outside them.
What the numbers show
In the general population, people who used cannabis were around twice as likely to have committed a violent act as those who did not. Among psychiatric patients, cannabis users were roughly 2.5 times as likely to be violent as other patients who did not use the drug.
For violence that resulted in a criminal conviction, cannabis users were three to four times as likely to have been convicted. The researchers analyzed self-reported violence and conviction-based violence separately, and where a study measured more than one kind of violence, they counted only the most serious.
Cannabis users were also about 1.5 times as likely to be victims of violence. That link was stronger for women than for men.
The association held in studies that followed people over time, although it was smaller in those long-term studies than in ones that captured a single point in time. Longitudinal designs generally carry more weight when researchers try to rule out chance findings.
"As a clinician, I've seen how heavy cannabis use can be a factor in violence," said Dr. Marta Di Forti, a co-author from IoPPN and the South London and Maudsley NHS Foundation Trust. "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 stigmatize people who use cannabis more broadly."
Sir Robin Murray, a professor at IoPPN and the study's senior author, pointed to the wider policy context. "As cannabis becomes more commercialized and legalized 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."
Association, not proof of cause
The researchers are explicit about the limits of their findings. The review shows an association between cannabis use and violence; it cannot prove that cannabis causes violent behavior. Cannabis use often occurs alongside other factors that may independently raise the risk of violence, including other drug and alcohol use and difficult social circumstances.
A meta-analysis of this kind combines results from many separate studies, which strengthens statistical power but inherits the weaknesses of the underlying data. Few of the studies included measured how much or how often people used cannabis, so the review cannot distinguish between occasional and heavy users. The findings on criminal convictions rest on a small number of studies.
There is also a timing problem. Most of the included studies predate the spread of high-potency cannabis products. The researchers suggest that daily use of today's stronger varieties could produce larger effects than their pooled numbers indicate, but no data in this review directly test that idea.
Practical implications
Despite these caveats, the authors argue the evidence is strong enough to inform practice. They say the findings support routinely asking about cannabis use when mental health services assess a person's risk of violence. They also recommend adding violence — both perpetrating it and experiencing it — to public health messaging about cannabis.
The study, led by Giulia Trotta and colleagues, appears in Psychological Medicine (2026), DOI: 10.1017/s0033291726105856.
via Medical Xpress (Source)
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