A new collaborative study led by the Mental Health Services in the Capital Region of Denmark and the National Institute on Drug Abuse (NIDA) at the National Institutes of Health focuses on screening, preventing, and treating cannabis use disorder among youths. This study also highlights the link between schizophrenia and cannabis use disorder, specifically among young men.
For the study, the international team analyzed 50 years of data representing more than 6 million people living in Denmark during that time. The study aimed to determine the percentage of schizophrenia cases that could be linked to cannabis use disorder across the entire population.
"The entanglement of substance use disorders and mental illnesses is a major public health issue, requiring urgent action and support for people who need it," said Nora Volkow, M.D., NIDA Director and one of the authors of this 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. The findings from this study are one step in that direction and can help inform decisions that health care providers may make in caring for patients, as well as decisions that individuals may make about their own cannabis use."
The 50 years of data were taken from national health registries in Denmark and included information regarding 6.9 million individuals between the ages of 16 and 49 from 1972 to 2021. This data allowed researchers to look not only at overall patterns of cannabis use disorder but to identify previously unknown associations between the disorder, age, and sex.
The results of the study found that there is 'strong evidence' linking cannabis use disorder to schizophrenia but that this link was significantly more noticeable in young men than women of the same age group. By the numbers, the researchers estimate that up to 30% of schizophrenia cases among young men (aged 21-30) might be attributed to cannabis use disorder and, therefore, could have been preventable with treatment for the initial cannabis use disorder. The researchers go on to refer to cannabis use disorder as a "major modifiable risk" in the development of schizophrenia within this population and that the risk will only increase with higher THC concentration in cannabis products.
The study's lead author, Carsten Hjorthøj, Ph.D., noted that legalization had impacted the public perception of psychoactive substances like cannabis, blinding people to their potential harm if misused. They noted, "This study adds to our growing understanding that cannabis use is not harmless, and that risks are not fixed at one point in time."