A systematic review of 15 studies found associations between cannabis use and aggression or violence in people with PTSD and psychotic-spectrum disorders, but methodological limitations prevent causal conclusions.
Clinicians treating psychiatric patients who use cannabis, and researchers studying the behavioral effects of cannabis in mental illness.
Longitudinal association found specifically in psychotic-spectrum disorders
What the researchers found
Cross-sectional associations between cannabis use and aggression/violence were found in PTSD samples. Longitudinal associations were observed in psychotic-spectrum disorders. However, uncontrolled confounding factors in most studies preclude causal conclusions.
Why it matters
Understanding whether cannabis increases aggression risk in people with psychiatric conditions is critical for clinical decision-making, but this review shows the evidence is not yet strong enough to draw firm conclusions.
The numbers in context
391 papers identified, 15 met inclusion criteria. Cross-sectional associations found in PTSD samples. Longitudinal associations found in psychotic-spectrum disorders.
How the study worked
Systematic review following PRISMA guidelines, searching PubMed, Google Scholar, MEDLINE, and PsycINFO from inception to January 2022. Of 391 papers, 15 met inclusion criteria examining aggression/violence in people with psychiatric diagnoses who use cannabis.
What this study cannot tell us
Only 15 studies met criteria. Most had uncontrolled confounders. The review mixed cross-sectional and longitudinal designs. Different definitions of aggression and violence were used across studies.
How to read the evidence
Moderate: systematic review with PRISMA methodology, but limited by small number of included studies and their methodological weaknesses.
When this study was published
Published in 2022.
The bigger picture
As cannabis use becomes more common, including among people with psychiatric conditions, understanding its relationship to aggression and violence becomes increasingly important for clinicians and patients alike.
Questions still open
- Does cannabis directly increase aggression in vulnerable populations, or do shared risk factors explain both? Could certain cannabis products or doses be more problematic? Would controlled studies show different results?
Common questions
Does cannabis make people aggressive?
Which psychiatric conditions showed the strongest link?
What would it take to prove causation?
Read the original research
Does cannabis use predict aggressive or violent behavior in psychiatric populations? A systematic review.
The American journal of drug and alcohol abuse, 48(6), 631-643
Citation
Sorkhou, Maryam; Johnstone, Samantha; Kivlichan, Ashley E; Castle, David J; George, Tony P. (2022). Does cannabis use predict aggressive or violent behavior in psychiatric populations? A systematic review.. The American journal of drug and alcohol abuse, 48(6), 631-643. https://doi.org/10.1080/00952990.2022.2118060
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