can profoundly affect people’s lives. People with cannabis use disorder are unable to stop using cannabis, despite the negative consequences in their lives. Schizophrenia is a serious mental illness that affects the way a person thinks, feels, and behaves. People with schizophrenia may seem to have lost touch with reality, and the symptoms of schizophrenia can make it difficult to participate in normal, everyday activities. However, there are effective treatments for both cannabis use disorder and schizophrenia.
“The intermingling of substance use disorders and mental illness is a major public health problem that requires urgent action and support for people who need it,” said NIDA director and study co-author Nora Volkow, MD. it is critical that we expand prevention, screening, and treatment for people who may experience mental illness related to cannabis use. patients, as well as the decisions individuals can make about their cannabis use.”
Previous studies have shown that daily or near-daily cannabis use, cannabis use disorder, and new schizophrenia diagnoses are higher among men than among women, and that early, frequent cannabis use is associated with an increased risk of developing schizophrenia. However, few studies have examined population-level differences in the association between cannabis use disorder and schizophrenia among different gender and age groups.
To address this research gap, investigators analyzed data from nationwide health registries in Denmark, which included health record data from more than 6.9 million people aged 16 to 49 between 1972 and 2021. examined how the association between cannabis use disorder and schizophrenia varied by gender and age group, and how these differences changed over time.
Although there are many risk factors associated with schizophrenia, the researchers in this study sought to estimate the proportion of all schizophrenia cases specifically attributable to cannabis use disorder across gender and age groups at the population level. The research team estimated that 15% of schizophrenia cases among men aged 16-49 could be prevented in 2021, compared to 4% among women aged 16-49, by preventing cannabis use disorder. For young men aged 21–30, they estimated that the preventable incidence rate of schizophrenia related to cannabis use disorder could be as high as 30%. The authors emphasize that cannabis use disorder appears to be a major modifiable risk factor for schizophrenia at the population level, particularly among young men.
The authors note that this increase is likely due to the higher potency of cannabis and the increase in the number of diagnosed cannabis use disorders over time.
“Increasing legalization of cannabis over the last few decades has made it one of the most widely used psychoactive substances in the world, but has also reduced the public’s perception of its harm. This study adds to our growing understanding that cannabis use is not harmless, and that these risks are not identified overnight,” Carsten Hjorthøj , Ph.D., lead author of the study and associate professor of Mental Health Services in the Capital Region of Denmark and the University of Copenhagen.
The authors note that further research is needed to examine potential differences in the potential and frequency of cannabis use between young men and women, and to explore the mechanisms underlying young men’s greater susceptibility to the schizophrenic effects of cannabis. The association of cannabis potency with cannabis use disorder and psychosis can help inform public health policy; policies regarding the sale and access of cannabis; and efforts to effectively prevent, screen, and treat cannabis use disorder and schizophrenia.