Question:  What is the risk of developing schizophrenia spectrum disorder following an emergency department (ED) visit caused by substance use with and without psychosis?

Findings:  In this cohort study of 9.8 million people, individuals with an ED visit for substance-induced psychosis or substance use without psychosis were at increased risk of developing schizophrenia spectrum disorder within 3 years relative to the general population.

Meaning:  These findings suggest that people who present to the ED for substance use, with or without psychosis, are at increased risk of developing schizophrenia spectrum disorder.

Abstract

Importance:  Episodes of substance-induced psychosis are associated with increased risk of developing a schizophrenia spectrum disorder. However, there are limited data on the transition risk for substance use without psychosis.

Objectives:  To quantify the risk of transition to schizophrenia spectrum disorder following an incident emergency department (ED) visit for (1) substance-induced psychosis and (2) substance use without psychosis and to explore factors associated with transition.

Results:  The study included 9 844 497 individuals, aged 14 to 65 years (mean [SD] age, 40.2 [14.7] years; 50.2% female) without a history of psychosis. There were 407 737 individuals with an incident ED visit for substance use, of which 13 784 (3.4%) ED visits were for substance-induced psychosis. Individuals with substance-induced psychosis were at a 163-fold (age- and sex-adjusted hazard ratio [aHR], 163.2; 95% CI, 156.1-170.5) increased risk of transitioning, relative to the general population (3-year risk, 18.5% vs 0.1%). Individuals with an ED visit for substance use without psychosis had a lower relative risk of transitioning (aHR, 9.8; 95% CI, 9.5-10.2; 3-year risk, 1.4%), but incurred more than 3 times the absolute number of transitions (9969 vs 3029). Cannabis use had the highest transition risk among visits with psychosis (aHR, 241.6; 95% CI, 225.5-258.9) and the third-highest risk among visits without psychosis (aHR, 14.3; 95% CI, 13.5-15.2). Younger age and male sex were associated with a higher risk of transition, and the risk of male sex was greater in younger compared with older individuals, particularly for cannabis use.

Conclusions and Relevance:  The findings of this cohort study suggest that ED visits for substance use were associated with an increased risk of developing a schizophrenia spectrum disorder. Although substance-induced psychoses had a greater relative transition risk, substance use without psychosis was far more prevalent and resulted in a greater absolute number of transitions. Several factors were associated with higher transition risk, with implications for counseling and early intervention

(Source:  JAMA Psychiatry | JAMA Network 2023)

A study by McLean Hospital’s Mary Kathryn Dahlgren, PhD, Staci Gruber, PhD, and their team from McLean’s Cognitive and Clinical Neuroimaging Core and the Marijuana Investigations for Neuroscientific Discovery (MIND) program, has found that recreational cannabis use affects driving ability even when users are not intoxicated by marijuana.

Published in the Drug and Alcohol Dependence journal, the study “Recreational Cannabis Use Impairs Driving Performance in the Absence of Acute Intoxication,” finds that in addition to chronic, heavy, recreational cannabis use being associated with poorer driving performance in non-intoxicated individuals compared to non-users, the researchers linked earlier onset of marijuana use (under age 16) to worse performance.

Study at a Glance

• McLean researchers have discovered that recreational marijuana use affects driving ability even when users are not intoxicated
• The study, conducted through driving simulation, concluded that chronic, heavy, recreational marijuana use was associated with worse driving performance in non-intoxicated drivers compared to non-using healthy control participants
• Cannabis users had more accidents, drove at higher speeds, and drove through more red lights than non-users
• Earlier onset of marijuana use (regular use prior to age 16) was associated with poorer driving performance
• Findings may be reflective of increased impulsivity in those who initiate substance use during adolescence; further research will explore this association

Recreational cannabis use has expanded across the United States in the last several decades and so has public concern about the substance’s impact on activities that present safety issues.

While several studies have examined the direct effect of cannabis intoxication on driving, no other studies until now have examined the effects on driving in heavy marijuana users who are not high.

Gruber, who is among the world’s foremost experts in the cognitive effects of marijuana, said the idea that differences can be detected in sober cannabis users may be surprising to the public.

“People who use cannabis don’t necessarily assume that they may drive differently, even when they’re not high,” she said. “We’re not suggesting that everyone who uses cannabis will demonstrate impaired driving, but it’s interesting that in a sample of non-intoxicated participants, there are still differences in those who use cannabis relative to those who don’t.”

Also see

• Cannabis use altering key functions like three-dimensional vision
• 'Medicinal’ Cannabis & Driving – Is it an Issue?

For Complete Research

“Global researchers are saying that today’s cannabis, is the singular most important link to youth mental health illness epidemic we have in this country.” [USA]

Marijuana companies are using the same manipulative tactics used by tobacco companies of the past. In fact, it’s the same exact playbook: advertising the product as medicine, using child-like messaging, and targeting people of color. Decriminalizing marijuana, for example, is important in getting closer to social justice equity, but that narrative often gets conflated with legalization and glamorization. Kevin Sabet Ph.D, President & CEO of Smart Approaches to Marijuana, sheds light on the detrimental societal impacts of marijuana and unveils the truths obscured by its glamorized portrayal.

View video

Research team discovered that individuals who used cannabis long-term (for several years or more) and heavily (at least weekly, though a majority in their study used more than four times a week) exhibited impairments across several domains of cognition. Long-term cannabis users' IQs declined by 5.5 points on average from childhood, and there were deficits in learning and processing speed compared to people that did not use cannabis…The study also found that people who knew these long-term cannabis users well observed that they had developed memory and attention problems. The above findings persisted even when the study authors controlled for factors such as dependence on other drugs, childhood socioeconomic status, or baseline childhood intelligence.

The impact of cannabis on cognitive impairment was greater than that of alcohol or tobacco use. Long-term cannabis users also had smaller hippocampi (the region of the brain responsible for learning and memory). https://www.health.harvard.edu/blog/cognitive-effects-of-long-term-cannabis-use-in-midlife-202206142760

When Kalpit Sharma started smoking cannabis, he thought it was just part of "living his life" as a university student. After all, he had been told that the drug was relatively harmless.

That all changed in the summer of 2021, when he started hearing voices in his head.

"I would bike around, and the chain of the bike, it came off. And I thought that I could speak to birds, and birds were telling me how to put the chain back on," said Sharma, who was studying at York University in Toronto at the time.

Those voices are known as auditory hallucinations — a hallmark of psychosis. When they became more frequent and insistent, he went to the Centre for Addiction and Mental Health for an assessment.

Sharma was shocked when he was told that he had been exhibiting signs of psychosis — and eventually he was diagnosed with schizophrenia.

In 2023, Myran co-authored two studies looking into the connection between cannabis and psychosis. They found a 220 per cent increase in emergency room visits in Ontario for cannabis-induced psychosis between 2014 and 2021 — with the number rising from about 400 people to about 1,400 over that seven-year period.

"For men aged 14 to 24, the risk of developing schizophrenia rises to over 40 per cent within three years" of showing up in an ER for cannabis-induced psychosis, he said.

Myran was also lead author of a separate study released in early February that found 27.5 per cent of people who visited an emergency room for cannabis use developed an anxiety disorder for the first time within three years. For complete article including videos go to https://www.cbc.ca/radio/whitecoat/cannabis-induced-psychosis-bad-trip-1.7116217

RELATED STORIES

• 5 years of legal cannabis: fewer charges, many hospitalizations and more than a few questions
• 'The world has changed dramatically': 5 years of legal cannabis in northern Ontario
• The razzle-dazzle days of Canada's cannabis industry are over as pot industry faces downturn
• Cannabis use sending more pregnant Canadians to hospital, new study finds
• The pros, cons and unknowns of legal cannabis in Canada 3 years later