New Study Warns Psychosis Is Increasing And Cannabis May Be A Factor As One Group Faces Higher Risk

A new study suggests cannabis use could be linked to a worrying rise in psychosis diagnoses among young people. Researchers believe the trend deserves closer attention due to how quickly the numbers have changed.

Between 1992 and 2023, the study reviewed health data from 12 million people who were born between 1960 and 2009 and lived in Ontario, Canada. This wide time span allowed researchers to compare multiple generations.

A sharp increase in people being diagnosed with psychotic disorders led researchers to explore possible causes. They pointed to growing use of substances such as cannabis, hallucinogens, and stimulant drugs as potential contributors.

The study, published in The Canadian Medical Association Journal, found a 60 percent increase in psychotic disorder diagnoses among people aged 14 to 20 between 1997 and 2023. During the same period, diagnosis rates declined in other age groups.

Researchers also found that compared to people born in the late 1970s, this younger group was twice as likely to receive a psychotic disorder diagnosis. That contrast has raised concern among experts.

When examining possible reasons for the rise in younger people, researchers pointed to several factors. These included neonatal health issues and having an older father, but cannabis use was also identified as a possible influence.

The Canadian study linked cannabis usage to psychosis diagnosis increases Getty Stock Images

Dr. Daniel Myran, one of the study’s authors, said he joined the research because of concerns that cannabis legalization could worsen psychosis diagnosis rates.

"I was expecting to see some increases in these younger folks, but I was quite surprised by the scale," he told The New York Times.

"I think that there is a group of individuals who develop psychosis because of substance use, who in its absence would not have," he explained.

"The interesting question is, how much of psychosis is caused by a modifiable substance use? Are these edge scenarios, where it's pretty rare? Or is it actually quite frequent?"

Across the full 31-year period covered by the study, only 0.9 percent of people were diagnosed with a psychotic disorder. Researchers noted that this shows psychosis remains uncommon overall.

In 2024, 41 percent of Canadians aged 16 to 19 reported using cannabis at least once a year. This figure is up five percent since legalization in 2018, according to the Canadian Cannabis Survey.

The researchers revealed those between 14 and 20 were twice as likely to be diagnosed Getty Stock Images

The study focused on conditions such as schizophrenia, which is marked by delusions, along with other psychotic diagnoses.

The biggest increase came from cases labeled as psychosis not otherwise specified. This diagnosis applies when psychotic symptoms are present but do not meet the criteria for schizophrenia.

While Dr. Myran said there is no single piece of evidence that proves cannabis is the cause, he believes substance use during teenage years could result in structural changes within the brain.

He said: "You go to the idea that neurons that fire together wire together. Your brain is quite plastic, and if we have substance use that's causing hallucinations, if you have ongoing activation and firing and that kind of stuff, it can change your brain."

If you want friendly, confidential advice about drugs, you can call American Addiction Centers at (313) 209-9137 at any time, or reach out through their website.