Cannabis use associated with violence perpetration and victimization in large review

A review led by King's College London researchers combined 63 studies involving more than 265,000 people to examine associations between cannabis use and violence perpetration and victimization. Published in Psychological Medicine, it analyzed general-population and psychiatric-care samples separately. Violence included physical, sexual and psychological acts, within and outside intimate relationships; researchers also distinguished self-reported violence from criminal convictions.

Cannabis users in the general population were reported to be approximately twice as likely to have committed violence as nonusers. Among people receiving psychiatric care, the corresponding association was approximately 2.5-fold. Cannabis use was associated with approximately 1.5-fold greater likelihood of victimization, with a stronger association among women. Violence-related convictions were three to four times as likely among users, although this finding came from relatively few studies. Associations persisted in longitudinal studies but were smaller than in cross-sectional studies.

The authors recommend routinely asking about cannabis use during violence-risk assessments in mental health services. However, alcohol use, other drug use and social adversity may contribute to the observed associations; the review does not establish that cannabis causes violence. Few studies measured consumption frequency or quantity, and most preceded widespread high-potency products. This account is based on a university-provided news report, which does not provide absolute risks or confidence intervals. Funding came from the NIHR Maudsley Biomedical Research Centre and Medical Research Council.