New research suggests young men with cannabis use disorder have the highest risk of developing schizophrenia.
A recent study published in the journal Psychological Medicine analyzed the health records of more than 6 million Danes over five decades. Researchers found a strong association between cannabis use disorder and schizophrenia, especially in men aged 21 to 30.
Using statistical models, the study estimated up to 30 per cent of schizophrenia cases in young men could have been prevented by averting cannabis use disorder.
“Cannabis use disorder and schizophrenia are serious but treatable, mental disorders that can profoundly impact people’s lives,” said Dr. Nora Volkow, director of the U.S. National Institute on Drug Abuse, which co-authored the study.
“As access to potent cannabis products continues to expand, it is crucial that we also expand prevention, screening, and treatment for people who may experience mental illnesses associated with cannabis use.”
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Previous research shows higher rates of cannabis use disorder and schizophrenia diagnoses in men, and that frequent, early cannabis use increases schizophrenia risk. However, few studies examined how the relationship varies by sex and age.
The Danish study looked at records of 6.9 million Danes aged 16 to 49 between 1972 and 2021. Researchers estimated 15 per cent of schizophrenia cases in men and four per cent in women could have been prevented by addressing cannabis use disorder. For men 21 to 30, the figure was 30 per cent.
Study co-author Carsten Hjorthøj, an associate professor at the Mental Health Services in the Capital Region of Denmark, said cannabis legalization and perceptions of its harmlessness are concerning given the potential risks, especially for young men.
“This study adds to our growing understanding that cannabis use is not harmless and that risks are not fixed at one point in time,” he said.