People who use cannabis face a significantly higher likelihood of both committing violent acts and experiencing violence themselves, according to a systematic review and meta-analysis published in Psychological Medicine. Researchers pooled data from 63 studies encompassing more than 265,000 individuals to evaluate the relationship between cannabis use and violent behavior across both general populations and psychiatric care settings.
How Cannabis Use Correlates With Committing and Experiencing Violence
The research team, based at the Institute of Psychiatry, Psychology & Neuroscience (IoPPN) at King’s College London, utilized the World Health Organization’s broad definition of violence. This framework covers physical, sexual, and psychological aggression directed toward others, occurring both inside and outside of relationships. Investigators analyzed self-reported violence alongside incidents that resulted in criminal convictions, prioritizing the most serious offense when studies recorded multiple types.
In the general population, individuals who used cannabis were approximately twice as likely to commit a violent act compared to non-users. Among patients receiving psychiatric care, cannabis users showed an even greater disparity, running roughly two and a half times as likely to be violent as psychiatric patients who did not use the substance. Cannabis users faced roughly a one-and-a-half times higher risk of being victims of violence, with this particular link proving stronger for women than for men.
When examining severe legal outcomes, the disparity widened further. Individuals who used cannabis were three to four times as likely to have a criminal conviction for a violent offense.
Clinical Insights and Public Health Implications
"As a clinician, I’ve seen how heavy cannabis use can be a factor in violence," said Dr. Marta Di Forti, co-author of the study from the IoPPN at King’s College London and the South London and Maudsley NHS Foundation Trust. "Although we have long hesitated to overstate the connection, this extensive evaluation enables us to address the dangers with greater assurance while avoiding any broad stigmatization of cannabis consumers."
Professor Sir Robin Murray, senior author of the study from King’s College London, noted that longitudinal studies tracking people over time confirmed the link, though effect sizes were smaller than in cross-sectional studies examining a single point in time. Murray drew attention to the changing worldwide perception and regulation of the substance: "Discussions regarding the dangers of marijuana tend to center primarily on individual consumers as legalization and commercial expansion spread globally. The current analysis highlights that the potential for violence, encompassing both perpetration and victimization, must be included in those discussions as well."
Based on these findings, the study authors recommend routinely screening for cannabis use during violence risk assessments in mental health services. They also advocate for incorporating the risk of violence into broader public health messaging regarding cannabis.
Study Limitations and Unmeasured Variables
The researchers noted that the review demonstrates an association rather than direct causation. Cannabis use frequently co-occurs with other risk factors for violence, including alcohol consumption, the use of other illicit substances, and challenging socioeconomic circumstances.
Additional methodological limitations include a lack of precise measurement regarding consumption amounts or frequencies in most reviewed studies. Data concerning criminal convictions derived from a limited subset of the analyzed research. The investigators also noted that most included studies took place before the widespread availability of high-potency cannabis strains, suggesting that daily use of modern, highly potent products could yield even stronger effects.
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