A recent study conducted in Denmark with over six million participants has revealed a significant association between cannabis use disorder and the development of bipolar disorder and depression. While the study does not establish a definitive causal relationship between cannabis use and these mental health conditions, researchers caution against unchecked cannabis use and urge careful consideration in discussions about legalization.
The research indicates that individuals with cannabis use disorder are at a heightened risk of experiencing bipolar disorder and depression. Cannabis, one of the most widely used illegal substances worldwide, appears to be more closely connected to mental disorders than previously believed, according to this new Danish investigation.
Examining register data from over six million Danish citizens, the study shows that cannabis use disorder is associated with an increased risk of both psychotic and non-psychotic depression, as well as bipolar disorder.
Lead author Oskar Hougaard Jefsen, a PhD student from the Department of Clinical Medicine at Aarhus University, emphasizes the significance of their findings. “When we account for variables such as gender, age, socioeconomics, and family history, we observe that cannabis use disorder is linked to nearly twice the risk of developing depression and two to three times higher risk of developing bipolar disorder in both men and women,” says Jefsen. The study, which has just been published in the scientific journal JAMA Psychiatry, is believed to be the largest investigation of its kind exploring the association between cannabis use disorder and affective disorders.
While one in three Danes under the age of 25 reportedly consume cannabis, the study exclusively focuses on individuals with significant cannabis use leading to a registered substance use disorder. This includes individuals who have sought substance abuse treatment or engaged with other parts of the healthcare system.
As more countries move towards legalizing cannabis, mounting evidence supports the notion that extensive cannabis use may have adverse effects on mental health. Previous studies have suggested a connection between cannabis use disorder and an increased risk of developing schizophrenia. However, investigations into the risks of other mental disorders have been limited until now.
Researchers from Aarhus University and the University of Copenhagen analyzed data from various Danish nationwide registers, including the National Patient Register, the Danish Psychiatric Central Research Register, and the Danish Register of Pharmaceutical Sales.
Jefsen notes the implications of their study on cannabis use regulation and legalization discussions. “Our findings suggest that cannabis use disorder is also associated with an increased risk of developing depression and bipolar disorder. This calls for caution in cannabis use, particularly for individuals at higher risk of mental illness, as well as for policymakers and decision-makers deliberating the legalization of cannabis,” he says.
In Denmark, since 2018, general practitioners have been able to prescribe cannabis-based drugs to patients as part of a trial scheme, while companies and individuals can also produce cannabis for medicinal or industrial purposes.
Jefsen emphasizes the need for further research to identify individuals for whom cannabis may be particularly harmful, which could aid in strengthening preventive measures. He also highlights the necessity of gaining more knowledge about the effects of different cannabis use levels on the brain, cognition, behavior, and identifying risk factors associated with the transition from cannabis use disorder to psychiatric disorders.
It is important to note that while the study provides indications, it does not offer definitive proof that cannabis causes these mental disorders, as Jefsen points out. For instance, it is possible that some individuals in the study may have had undiagnosed depression or bipolar disorder, leading to the development of cannabis use disorder, rather than the other way around.
Jefsen acknowledges the unique advantages of Danish register data, which considers crucial factors influencing the results. However, he highlights that conclusive evidence would necessitate an unethical randomized controlled trial in which individuals would have to consume large amounts of cannabis to determine whether it increased their long-term risk of developing mental illness.
The study, a register-based epidemiological cohort study, involved 6,651,765 individuals born in Denmark before 2006, who resided in the country between 1995 and 2021. The research team consisted of Associate Professor Carsten Hjorthøj, Senior Researcher Annette Erlangsen, and Clinical Professor Merete Nordentoft, all from the University of Copenhagen.
Reference: “Cannabis Use Disorder and Subsequent Risk of Psychotic and Nonpsychotic Unipolar Depression and Bipolar Disorder” by Oskar Hougaard Jefsen, MD; Annette Erlangsen, PhD; Merete Nordentoft, DMSc; and Carsten Hjorthøj, PhD, 24 May 2023, JAMA Psychiatry.
DOI: 10.1001/jamapsychiatry.2023.1256
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Frequently Asked Questions (FAQs) about cannabis use disorder
What did the Danish study find regarding cannabis use disorder and mental health conditions?
The Danish study found that cannabis use disorder is significantly associated with an increased risk of developing bipolar disorder and depression. Individuals with cannabis use disorder had almost twice the risk of developing depression and two to three times higher risk of developing bipolar disorder, even when accounting for various factors such as gender, age, socioeconomics, and family history.
Does the study prove that cannabis use causes bipolar disorder and depression?
No, the study does not provide conclusive evidence that cannabis use causes bipolar disorder and depression. While the study indicates a strong link between cannabis use disorder and these mental health conditions, it cannot establish a definitive causal relationship. Other factors, such as undiagnosed depression or bipolar disorder leading to cannabis use disorder, could also be at play.
What are the implications of the study’s findings?
The study’s findings highlight the need for caution in cannabis use, particularly for individuals at a higher risk of mental illness. It also calls for careful consideration in debates surrounding the legalization of cannabis. Policymakers and decision-makers should take into account the potential risks associated with cannabis use disorder and its impact on mental health when formulating regulations.
Are there other mental health disorders associated with cannabis use disorder?
The study primarily focused on the association between cannabis use disorder and bipolar disorder and depression. While previous research has linked cannabis use disorder with an increased risk of developing schizophrenia, the study indicates that other mental disorders, apart from bipolar disorder and depression, have been sparsely studied in this context. Further research is needed to explore potential links with other mental health conditions.
How was the study conducted?
The study utilized register data from over six million Danish individuals. Researchers analyzed various nationwide registers, including the National Patient Register, the Danish Psychiatric Central Research Register, and the Danish Register of Pharmaceutical Sales. This register-based epidemiological cohort study aimed to explore the relationship between cannabis use disorder and subsequent risk of bipolar disorder and depression.
5 comments
hold up, this study doesn’t mean that cannabis causes mental disorders. it just shows a link, so let’s not jump to conclusions. there could be other factors at play here. but it’s still important to be cautious and consider the risks, especially if you’re already at risk for mental illness.
this study is just another attempt to demonize cannabis. they can’t prove causation, so why are they trying to scare people? cannabis has been used for centuries without all these mental health problems. let’s focus on responsible use and education instead of fear-mongering.
wow i didn’t know that cannabis use disorder can increase the risk of bipolar disorder and depression. that’s pretty serious stuff! we should be careful with the use of cannabis and think twice before legalizing it.
it’s good that more countries are legalizing cannabis, but studies like this make me think twice. we need more research to fully understand the effects of cannabis on mental health. maybe there are certain people who are more vulnerable to its negative effects. better safe than sorry!
man, it’s crazy how many people in Denmark smoke cannabis. one in three under 25? that’s a lot! but this study focuses on people with a substance use disorder, so it doesn’t represent all cannabis users. i wonder how different the results would be if they looked at all cannabis users.