Teens who use marijuana are more likely to suffer psychotic disorders, study finds

Teens who used cannabis in the past year had a dramatically higher rate of developing a psychotic disorder, according to a study published Wednesday.

The study, led by researchers at the University of Toronto, found an 11 times greater risk of developing a psychotic disorder among teens who used cannabis compared to those who did not. When the analysis was limited to just emergency room visits and hospitalizations, there was a 27-fold increase in psychotic disorders in teenagers who used the drug.

“When I see young people with psychotic symptoms, they almost always use a lot of cannabis,” said Dr. Leslie Hulvershorn, a child psychiatrist and chair of the department of psychiatry at Indiana University, who was not involved in the study. “It would be unusual to see someone presenting with psychotic symptoms in a hospital and not have smoked cannabis.”

The article contributes to the growing body of research linking cannabis to an increased risk of psychotic disorders, especially in adolescence. Marijuana use, especially higher potency products, has been linked to a variety of mental health disorders, including schizophrenia, anxiety, and depression.

“I think there’s enough evidence that we can make recommendations that teenagers probably shouldn’t consume cannabis,” said the study’s lead author, Andre McDonald, a postdoctoral researcher at McMaster University in Hamilton, Ontario. “If we can somehow ask teenagers to delay using it until their brain develops a little more, I think that would be good for public health.”

Although most teens who use cannabis do not develop psychotic disorders, McDonald said, the findings are concerning given how debilitating these conditions can be.

The new study, like previous research on marijuana and psychosis, does not directly prove that marijuana is causing psychotic disorders. While it’s possible that teens prone to developing psychotic disorders are also more likely to use cannabis, it’s unlikely given how striking the association was, Hulvershorn said.

“The magnitude of the effect here is hard to believe that it’s not related to cannabis,” Hulvershorn said.

There was no association between cannabis use and psychotic disorders in people aged 20 to 33.

“There’s something about this stage of brain development that we haven’t yet fully characterized – where there’s a window of time in which cannabis use can increase the risk of psychosis,” said Dr. Kevin Gray, professor of psychiatry and director of science at the addiction. from the Medical University of South Carolina, who was not involved in the study. “This study really highlights that delaying cannabis use until age 20 can mitigate one of the potentially most serious risks.”

The Biden administration has been moving toward reclassifying marijuana from Schedule I to the less dangerous Schedule III, which would also recognize its medical benefits at the federal level. While the potential change is expected later this year, cannabis is currently legal in 24 states for recreational use.

Marijuana use among high school students has remained stable in the last years. Nearly 1 in 3 12th graders reported using it in the past year, according to the 2023 Monitoring the Future Survey, an annual survey that measures drug and alcohol use among teenage students nationwide.

The new research, published in the respected journal Psychological Medicine, includes data from more than 11,000 teenagers and young adults aged 12 to 24 at the start of the study.

The authors drew data from the Annual Canadian Community Health Survey, focusing on 2009 to 2012. Participants were followed for up to nine years after the initial survey to track any visits they might have made to doctors or emergency rooms or any time they were hospitalized. hospitals..

Of teens who were hospitalized or visited emergency rooms for psychotic disorders, about 5 in 6 reported prior cannabis use.

“We see time and time again that there is a developmental window of adolescence that is very high risk,” Gray said.

It’s not completely clear why, he added, but one theory is that disruptions in the endocannabinoid system in adolescence may make psychotic symptoms more likely. The endocannabinoid system is a complex signaling system in the brain that marijuana targets. This could make it more difficult to distinguish reality from what is going on inside the head, leading to symptoms such as hallucinations.

The authors did not specifically look at how the potency of marijuana products affected the risk of mental disorders, although previous research has found an increased risk.