Increased schizophrenia cases linked to cannabis use disorder: Study

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The number of schizophrenia cases linked to cannabis use disorder is on the rise, according to a recent study.

Researchers in Denmark found that over the past 25 years, schizophrenia diagnoses linked to marijuana use in the country had increased.

In 1995, 2% of schizophrenia diagnoses were associated with cannabis use disorder. In 2000, it increased to around 4%.

And since 2010, that number increased to 8%, according to the study.

“I think it is highly important to use both our study and other studies to highlight and emphasize that cannabis use is not harmless,” said researcher Carsten Hjorthoj, one of the authors of the study published in the medical journal, JAMA Psychiatry, told CNN.

“There is, unfortunately, evidence to suggest that cannabis is increasingly seen as a somewhat harmless substance,” added Hjorthoj, an associate professor at the Copenhagen Research Center for Mental Health. “This is unfortunate since we see links with schizophrenia, poorer cognitive function, substance use disorders, etc.”

Denmark has seen an increase in cannabis use and cannabis use disorder, according to the study. Unlike Canada, Denmark only allows people to use pot for medicinal purposes.

“Of course, our findings will have to be replicated elsewhere before firm conclusions can be drawn,” Hjorthoj said. “But I do feel fairly confident that we will see similar patterns in places where problematic use of cannabis has increased, or where the potency of cannabis has increased, since many studies suggest that high-potency cannabis is probably the driver of the association with schizophrenia.”

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Schizophrenia is a psychotic disorder with symptoms that include delusions, hallucinations and impaired cognitive ability. It has no cure and affects 20 million people around the world.

According to national data, one out of 100 Canadians have been diagnosed schizophrenia — 56% were men.

Between 2002 and 2016, that number has increased by an average of 3% per year in Canada.

According to the study, the findings could help explain the “general increase in the incidence of schizophrenia that has been observed in recent years” and provide some support that the “long-observed association between cannabis and schizophrenia is likely partially causal in nature.”

It should be noted the study assessed people diagnosed for cannabis treatment disorder, not general users of the drug.