The proportion of new schizophrenia cases linked to cannabis use in Ontario, Canada, increased from 4% prior to legalization to 10% following, reported a new study. The findings were published in Substance and Addiction.
Previous studies suggest that cannabis use is linked to the development or earlier onset of psychosis and schizophrenia and that more frequent use of higher-potency cannabis products is linked to a higher risk of schizophrenia. In the current study, researchers investigated whether an association exists between cannabis legislation in Ontario and the incidence of schizophrenia.
To do so, they analyzed health data from 2006 to 2022 including over 13.5 million people aged 14 to 65 years old in Ontario. None of the participants had a history of schizophrenia. The researchers analyzed associations between the diagnosis of cannabis use disorder and schizophrenia.
Among the population studied, 0.7% without cannabis use disorder developed schizophrenia, while the same was true for 8.9% of individuals with the disorder. The researchers further found that the percentage of all new cases of schizophrenia in Ontario who had received hospital care for cannabis use disorder prior to being diagnosed with schizophrenia rose from 7% to 16%.
While the authors noted that their study does not prove a causal link between heavy cannabis use and schizophrenia, they noted that heavy cannabis use worsens symptoms and prognosis for those living with schizophrenia.
“Our study highlights the growing public health challenge posed by the combination of increasingly high-potency cannabis and rising regular cannabis use,” said Dr. Daniel Myran, a Canada Research Chair in Social Accountability at the University of Ottawa, in a press release.
“The tripling of schizophrenia cases associated with a cannabis use disorder over the past 17 years and rising cases of psychosis underscores the urgent need for targeted prevention strategies, particularly for younger populations who appear to be at the greatest risk,” he added.
Sources: EurekAlert, Substance and Addiction
