Study Links Cannabis With Violence In Psychiatric Patients

Medical Marijuana

A new study released last week found that chronic use of cannabis increased violent tendencies in young people recently released from psychiatric care.

The research was conducted by Dr. Alexandre Dumais (MD, PhD, FRCPC, psychiatrist at the Institut Philippe Pinel) and Dr. Stéphane Potvin (PhD, professor at the Université de Montréal). They studied 1,136 patients aged between 18 and 40 who have diagnosed mental illnesses. Each patient, after their discharge from psychiatric care, came in for an appointment five times in the following year.

As published in Frontiers in Psychiatry, the study reports that patients who said during their appointment that they continued using cannabis increased their risk for violent behavior by 144%. In other words, the more these patients used cannabis during their year after release, the more likely they were to become violent.

Thus, the study claims that cannabis is an indicator of future aggression for people with mental illness. “Even though we observed that violent behaviour tended to decrease during follow-up periods, the association remained statistically significant,” wrote Dr. Dumais in the study.

The researchers also say their study confirms that sustained cannabis use has a detrimental affect on patients with mental illness. The data shows a stronger connection between cannabis and violence with these patients than with alcohol or cocaine, the researchers point out.

However, the researchers believe that this tendency towards aggression will fade over time. As patients move beyond a year from release, better embrace their treatment and receive greater help from friends and family, their violent tendencies will diminish, researchers say.

The study indicated that there is no reciprocal relationship between cannabis and violence. While use of the drug in recently released psychiatric patients did up the odds of violence, the more-violent patients did not gravitate towards marijuana with any noticeable increase.

What’s the reason for the spike in violent urges? Recent studies suggest that chronic cannabis users develop deficiencies in their prefrontal cortex, an area in the brain that impedes impulsive behaviors.

Kyle Swartz is editor of Cannabis Regulator. Reach him at or on Twitter at @kswartzz. Read his recent piece: Report Reveals What Fast Food Cannabis Users Prefer.