Marijuana and violence: How much more evidence do we need of the connection?

For decades, marijuana advocates have promoted the image of a harmless drug producing relaxation, laughter, and peaceful behavior. That image has helped normalize marijuana use and fuel a multibillion-dollar commercial industry.

But scientific research increasingly challenges this reassuring narrative.

A major systematic review and meta-analysis published last month in the journal Psychological Medicine examined 63 studies involving more than 265,000 participants. Researchers found significant associations between marijuana use and violence across both general-population and psychiatric samples.

Among the general population, marijuana users had approximately twice the odds of perpetrating violence. Among psychiatric patients, the odds were nearly two and a half times as high.

The association with marijuana use was even stronger — 3.75 times as high in the general population — in studies examining violence resulting in criminal convictions. And among psychiatric patients, the association between marijuana and criminal violence was 4.21 times as high.

These findings deserve national attention, but this is hardly the first warning. A 2020 meta-analysis published in the American Journal of Psychiatry examined 30 studies involving nearly 300,000 adolescents and young adults. Researchers found that the odds a subject committed physical violence more than doubled if he was a marijuana user. Other studies have identified associations between marijuana use and intimate-partner violence.

Research involving patients with schizophrenia has raised additional concerns. The connection between marijuana, serious psychiatric illness, and violence is particularly troubling. Nearly four........

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