• Posted May 22, 2024

Teen Cannabis Users' Risk for Psychosis May Be Stronger Than Thought: Study

Doctors have long known that excessive marijuana use can trigger psychosis, especially in the young. But new research suggests the link is stronger that ever imagined before.

Teens who use cannabis face 11 times the odds for a psychotic episode compared to teens who abstain from the drug, new Canadian research contends.

The teen years may be an especially vulnerable time in this regard, the researchers noted.

"We found a very strong association between cannabis use and risk of psychotic disorder in adolescence. Surprisingly, we didn't find evidence of association in young adulthood,"said lead author André McDonald, who led the study as part of his PhD work at the University of Toronto.

The findings were published May 22 in the journal Psychological Medicine. McDonald finished the research while at the Institute for Clinical Evaluative Sciences (ICES).

Psychotic episodes involve a dangerous psychiatric state in which people lose their connection with reality. These episodes can get so out of control that people may need hospitalization.

It's long been known that marijuana use can help trigger psychosis, and the potency of cannabis is much stronger now than in decades past, the Toronto investigators noted. They estimate that the average THC potency of cannabis in Canada rose from roughly 1% in 1980 to 20% in 2018. 

So how is all that super-strong weed affecting the developing brains of the teens who use it?

To find out, McDonald and his colleagues looked at survey data from over 11,000 youth in the Canadian province of Ontario, as well as provincial health service use records including hospitalizations, emergency department (ED) visits and outpatient visits.

They found a very strong link between hospital visits for psychosis and the use of marijuana by teens.

In fact, 5 of every 6 teens admitted to the hospital for a psychotic episode had a history of marijuana use, the study found.

In an ICES news release, McDonald stressed that "the vast majority of teens who use cannabis will not develop a psychotic disorder."

However, he also noted that, "according to these data, most teens who are diagnosed with a psychotic disorder likely have a history of cannabis use." 

The study could only show an association between weed use and psychosis, not cause-and-effect. It's possible that teens who were already vulnerable to psychosis were more prone to "self-medicating" with marijuana, for example. Genetics and personal traumas in the teens' lives might also play a role.

Still, the statistical link between marijuana use and psychotic episodes was so strong that it does give pause for thought, said study senior author Susan Bondy.

"As commercialized cannabis products have become more widely available and have a higher THC content, the development of prevention strategies targeting teens is more important than ever,"said Bondy, an affiliate scientist at ICES and an associate professor at the University of Toronto."¯ 

More information

Find out more about the marijuana-psychosis connection at the Child Mind Institute.

SOURCE: Institute for Clinical Evaluative Sciences, news release, May 22, 2024