New research examines impact of cannabis on mental health

Mar 22, 2024

In recent months, researchers from the Ottawa Hospital Research Institute have published several studies examining the association between cannabis use and mental health disorders. Led by Dr. Daniel Myran, a researcher with the Ottawa Hospital Research Institute and a family physician, the studies aim to examine potential health concerns of cannabis use following its legalization in 2018.  

 The first study, published in the medical journal Lancet, examined the connection between cannabis use and anxiety disorders. According to the results, individuals requiring emergency department treatment for cannabis use have a significantly higher risk of developing an anxiety disorder, as well as a higher risk of worsening symptoms for an already existing anxiety disorder.

The research involved analyzing health records from 12,099,144 individuals aged between 10 and 105 years of age across Ontario over the span of 2008 to 2019. The data gather was from individuals who had no prior history of being diagnosed with an anxiety disorder and was then compared to the general population.

As a result, the researchers found that 27.5% of individuals who visited a hospital for cannabis use were diagnosed with an anxiety disorder within three years of their hospital visit, compared to only 5.6% of the general population. It was found that individuals who visited a hospital for cannabis use also visited a hospital for an anxiety disorder within three years of the initial hospital visit, in contrast to 1.2% of the general population.

“ED visits for cannabis use were associated with an increased risk of having an incident healthcare visit for an anxiety disorder, particularly in young males. These findings have important clinical and policy implications given the increasing use of cannabis over time and trend towards legalization of cannabis,” the study authors concluded.

Two more studies, published in JAMA Psychiatry and Molecular Psychiatry, found that there was a 220% increase in emergency room visits in Ontario for cannabis-induced psychosis over the period spanning 2014 and 2021, increasing from 400 to about 1,400 people. In addition, the findings of this research study suggest that emergency room visits for substance use were associated with an increased risk of developing a schizophrenia spectrum disorder.

 “I think that people remain unaware of this connection between cannabis use and potential risk of chronic psychotic disorders,” said Dr. Myran in his interview with CBC News. “For men aged 14 to 24, the risk of developing schizophrenia rises to over 40% within three years of showing up in an ER for cannabis-induced psychosis,” he said.

Researchers also expressed concerns regarding high cannabis content in commercially sold cannabis-containing products. “It’s been around for centuries. True enough. But the product that we’re using today that’s available to our youth and young adults into the population today is completely different than even what it was 10, 15 years ago,” said Dr. Philip Tibbo, a professor and director of research in the department of psychiatry at Dalhousie University in Halifax, in his interview with CBC News.