Young Men With Cannabis Use Disorder Are At Increased Risk Of Schizophrenia: NIH Study

Cannabis use disorder and schizophrenia have been found to be linked among both men and women, but the link is much stronger among young men.

Young men who have cannabis use disorder, a mental disorder in which a person continues using cannabis (marijuana) despite their physical, psychological and social functioning being impaired, are at an increased risk of developing schizophrenia, compared to people who don't have this disorder. Schizophrenia is a chronic brain disorder in which people experience hallucinations, delusions and extremely disordered thinking, and are not able to think, feel and behave clearly as they interpret reality abnormally. Cannabis use disorder and schizophrenia have been found to be linked among both men and women, but the link is much stronger among young men, according to a US National Institutes of Health (NIH)-led study study. 

The study describing the findings was published May 4, 2023, in the journal Psychological Medicine. Researchers at the Mental Health Services in the Capital Region of Denmark, and the National Institute on Drug Abuse (NIDA), which is a part of NIH, analysed data which includes more than six million in Denmark, and spans over five decades, as part of the study. 

How the study was conducted

The aim of the study was to estimate the fraction of schizophrenia cases in the population that are linked to cannabis use disorder. 

The individuals analysed were aged 16 to 49 years at some point during 1972 to 2021, the study said. 

30% schizophrenia cases among young men could have been prevented by averting cannabis use disorder

If men aged 21 to 30 years averted cannabis use disorder, about 30 per cent of schizophrenia cases among them could have been prevented.  

While both cannabis use disorder and schizophrenia are serious mental illnesses, they can be treated. 

In an NIH statement, Nora Volkow, one of the co-authors on the paper, said the "entanglement" of substance use disorders and mental illnesses is a major public health issue, and requires urgent action and support for people who need it. She also said that as access to potent cannabis products continues to expand, it is crucial that prevention, screening and treatment for people who may experience mental illnesses with cannabis use are also expanded. 

In the statement, Volkow explained that the findings from the study are one step in that direction and can help inform decisions that health care providers may make in caring for patients. 

Significance of the new study

Men with daily or nearly daily cannabis use, and cannabis use disorder have higher new schizophrenia diagnoses than women having the disorder or using cannabis daily or nearly daily, according to previous research. Only a few studies have analysed the differences in the relationship between cannabis use disorder and schizophrenia across different sex and age groups at the population level, according to NIH. 

The study said that schizophrenia cases associated with cannabis use disorder have consistently increased over the past five decades. The higher potency of cannabis and increasing prevalence of diagnosed cannabis use disorder over time are the reasons behind this increase in schizophrenia cases. 

The authors concluded that a population level, one-fifth of cases of schizophrenia among young men can be prevented by averting cannabis use disorder, and that early detection and treatment of cannabis use disorder and policy decisions regarding the use and access of cannabis, particularly for people aged 16 to 25 years of age, are important to prevent schizophrenia.