Is Marijuana as healthy as we think? A new study from the National Institutes of Health (NIH) says young men between 21-30 who use Cannabis have higher risk of developing schizophrenia symptoms such as hallucinations, delusions, and extremely disordered thinking and behavior.

The study authors say “cannabis use is not harmless, and that risks are not fixed at one point in time.”

A new study by researchers at the Mental Health Services in the Capital Region of Denmark and the National Institute on Drug Abuse (NIDA) at the National Institutes of Health has found a strong association between cannabis use disorder and schizophrenia, particularly among young men.

The study, published in Psychological Medicine, analyzed detailed health records data from over 6 million people in Denmark over a 5-decade period to estimate the population-level fraction of schizophrenia cases that could be attributed to cannabis use disorder.

The study authors used statistical models to estimate that up to 30% of schizophrenia cases among men aged 21-30 might have been prevented by averting cannabis use disorder. While cannabis use disorder and schizophrenia are serious and treatable mental disorders, they can have a profound impact on people’s lives, making it difficult to participate in everyday activities. Effective treatments are available for both conditions, but the study’s findings raise important questions about the safety of cannabis use and the need for proactive prevention and treatment efforts.

The Link Between Cannabis Use Disorder and Schizophrenia

While previous studies have indicated higher rates of daily or near daily cannabis use, cannabis use disorder, and new schizophrenia diagnoses among men compared to women, few have examined the specific relationship across various population segments.

To bridge this research gap, investigators conducted a comprehensive analysis of nationwide health registers in Denmark, encompassing health records from over 6.9 million individuals aged 16-49 between 1972 and 2021. By utilizing this extensive longitudinal data, the researchers explored how the associations between cannabis use disorder and schizophrenia varied among different sex and age groups, and how these variations changed over time.

While schizophrenia is influenced by multiple risk factors, the study aimed to estimate the proportion of schizophrenia cases that could be attributed to cannabis use disorder at the population level across sex and age groups. The findings revealed that in 2021, approximately 15% of schizophrenia cases among men aged 16-49 could potentially have been prevented by averting cannabis use disorder, in contrast to 4% among women in the same age group. Notably, the study highlighted that young men aged 21-30 exhibited the highest proportion of preventable schizophrenia cases related to cannabis use disorder, potentially reaching up to 30%. This underscores the significance of cannabis use disorder as a modifiable risk factor for schizophrenia, particularly among young men in the general population.

The study further supports existing evidence suggesting a consistent increase in the proportion of new schizophrenia cases attributable to cannabis use disorder over the past five decades. The authors attribute this trend to factors such as the higher potency of cannabis and the growing prevalence of diagnosed cannabis use disorder over time.

“Increases in the legalization of cannabis over the past few decades have made it one of the most frequently used psychoactive substances in the world, while also decreasing the public’s perception of its harm,” remarks lead author Carsten Hjorthøj.

“This study adds to our growing understanding that cannabis use is not harmless, and that risks are not fixed at one point in time.”

Further research is needed to investigate the differences in cannabis consumption patterns between young men and women, and to better understand the mechanisms that make young men more vulnerable to the effects of cannabis on schizophrenia, according to the authors of the study. The study’s findings suggest that public health guidelines and policies on cannabis sales and access could be informed by the association of cannabis potency with cannabis use disorder and psychosis. The authors emphasize the importance of effective prevention, screening, and treatment efforts for cannabis use disorder and schizophrenia.

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