Teenagers who use marijuana more likely to suffer from psychotic disorders, study finds

Teenagers who used cannabis in the past year had a significantly higher rate of psychotic disorders, according to a study released Wednesday.

The study, led by researchers at the University of Toronto, found an 11 times higher risk of developing a psychotic disorder among adolescents who used cannabis compared to those who did not use it. When the analysis was limited to emergency room visits and hospitalizations, psychotic disorders were multiplied by 27 among adolescents 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. ‘study. “It would be unusual to see someone present to hospital with psychotic symptoms and not have smoked cannabis. »

The article adds to the growing body of research that links cannabis to an increased risk of psychotic disorders, particularly in adolescence. Marijuana use, especially high-potency products, has been linked to a variety of mental health disorders, including schizophrenia, anxiety, and depression.

“I think there is enough evidence that we can make recommendations that adolescents probably should not use cannabis,” said the study’s lead author, Andre McDonald, a postdoctoral researcher at the University McMaster in Hamilton, Ontario. “If we can get teens to delay drinking until their brains develop a little more, I think that would be good for public health.”

Although most adolescents who use cannabis will 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 causes psychotic disorders. While it’s possible that adolescents prone to developing psychotic disorders are also more likely to use cannabis, that’s unlikely because of the striking association, Hulvershorn said.

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

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

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

The Biden administration is moving toward reclassifying marijuana from Schedule I to the less dangerous Schedule III, which would also recognize its medical benefits at the federal level. Although this 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 recent years. Nearly 1 in 3 12th graders reported using it in the past year, according to the Monitoring the Future 2023 survey, an annual survey that measures drug and alcohol use among the nation’s teens .

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

The authors drawn from the Annual Canadian Community Health Survey, focused on the period 2009 to 2012. Participants were then followed up to nine years after the initial survey to track any visits they had may have had at the doctor or emergency room or whenever they were admitted to the hospital. hospitals..

Among adolescents hospitalized or visited the emergency room for psychotic disorders, approximately 5 out of 6 reported having already used cannabis.

“We keep seeing that this developmental window of adolescence is very high risk,” Gray said.

It’s not entirely clear why, he added, but one theory is that disruptions to the endocannabinoid system during adolescence might make psychotic symptoms more likely. The endocannabinoid system is a complex signaling system in the brain targeted by marijuana. This could make it harder to distinguish between reality and what’s going on in your head, leading to symptoms such as hallucinations.

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