Cannabis use disorder was not linked to violence in people with schizophrenia, but alcohol use disorder was | Research

The takeaway

Among 124 patients with schizophrenia in a high-security hospital, cannabis use disorder was not associated with impulsivity or violence, while alcohol use disorder was nearly four times more likely to be associated with violent behavior.

Forensic psychiatrists, clinical risk assessors, mental health professionals working with psychosis patients

Alcohol, not cannabis, was associated with violence in schizophrenia (OR=3.96)

What the researchers found

Violent and nonviolent psychotic patients had similar rates of cannabis use disorder. Cannabis was not associated with any dimension of impulsivity. In contrast, alcohol use disorder was associated with impulsive behavior and was nearly 4 times more likely in violent patients (OR=3.96). Cocaine use disorder was associated with proneness to boredom but not violence.

Why it matters

The common assumption that cannabis drives violence in people with psychosis is challenged by this data showing alcohol, not cannabis, is the substance associated with violent behavior in this high-risk population.

The numbers in context

124 patients; alcohol use disorder OR=3.96 for violence; cannabis use disorder not associated with violence or impulsivity; cocaine linked to proneness to boredom

How the study worked

Cross-sectional retrospective study of 124 patients with schizophrenia spectrum disorders in a high-security hospital, using standardized measures of violence history, impulsivity, psychopathy, substance use, and psychotic symptoms.

What this study cannot tell us

Cross-sectional design in a specialized high-security setting. Patients may underreport substance use. Results may not generalize to community-dwelling psychosis patients. Small sample size.

How to read the evidence

Cross-sectional study in a specialized high-security setting with standardized measures

When this study was published

Published in 2021. The relationship between substance use and violence in psychosis remains debated.

The bigger picture

This finding is important for clinical risk assessment. If practitioners focus on cannabis as a violence risk factor while underweighting alcohol, they may misjudge which patients are at highest risk.

Questions still open

Does this finding hold in community settings? Should clinical violence risk assessments weight alcohol more heavily than cannabis? Could cannabis use be a marker for other risk factors without being causal?

Common questions

Does cannabis make people with schizophrenia violent?

This study found no association between cannabis use disorder and violence or impulsivity in 124 schizophrenia patients. Alcohol use disorder, not cannabis, was the substance associated with violent behavior.

Which substance poses the greatest violence risk in psychosis?

In this high-security hospital study, alcohol use disorder was nearly four times more likely among violent patients. The authors recommend clinicians focus on alcohol abuse when assessing dangerousness in psychotic patients.

Read the original research

Lifetime Cannabis Use Disorder Is Not Associated With Lifetime Impulsive Behavior and Severe Violence in Patients With Schizophrenia Spectrum Disorders From a High-Security Hospital.

Journal of clinical psychopharmacology, 41(6), 623-628

View on PubMed ↗Publisher’s paper ↗

Citation

Comai, Stefano; Fuamba, Yves; Rivolta, Maria Chiara; Gobbi, Gabriella. (2021). Lifetime Cannabis Use Disorder Is Not Associated With Lifetime Impulsive Behavior and Severe Violence in Patients With Schizophrenia Spectrum Disorders From a High-Security Hospital.. Journal of clinical psychopharmacology, 41(6), 623-628. https://doi.org/10.1097/JCP.0000000000001493