Chronic Marijuana Use Tied to Mental Illnesses like Depression and Bipolar Disorder, Study Finds

  • Staff Consortium
  • July 07, 2023

Governor Albert Bryan, center left, listens to Telluride head of operations Rick Scicchitano, left, during a tour of the marijuana grow facility in Colorado on Wed., Oct. 27, 2021. By. ERNICE GILBERT, V.I. CONSORTIUM

A new study examining the connection between marijuana use and mental health disorders reveals significant potential risks associated with chronic use of the drug. This research throws a spotlight on the potential public health issues that may accompany the growing legalization of marijuana. 

Governor Albert Bryan in January 2023 signed into law the Virgin Islands Cannabis Use Act (Act 8680), which allows for the legal use by adults of marijuana for recreational, medicinal and other purposes. The law also greenlights the legal distribution of marijuana in the U.S. Virgin Islands.

The study, conducted by Dr. Oskar Hougaard Jefsen of Aarhus University and his team, scrutinized the medical records of all Danish citizens above the age of 16, approximately 6.5 million individuals, between 1995 and 2021. The study, published in JAMA Psychiatry, sought patterns of diagnosis, hospitalization, and treatment for substance use over this period, according to a report in the Wall Street Journal.

The researchers found that individuals previously diagnosed with cannabis use disorder were nearly twice as likely to later be diagnosed with clinical depression. The Centers for Disease Control and Prevention defines cannabis use disorder as a craving for marijuana, using it more often than intended, spending a significant amount of time using it, and experiencing disruptions in relationships and work due to usage.

The research further indicated that individuals with cannabis use disorder were up to four times as likely to be diagnosed later with bipolar disorder with psychotic symptoms. The risk was higher in men than in women, and the risk grew in relation to the quantity of cannabis consumed. The study did not differentiate between various forms and concentrations of cannabis.

While the connection is robust, the researchers noted that they could not definitively state whether chronic and heavy cannabis use induces psychosis, or whether individuals prone to mental illness are more likely to be heavy users. However, the study's extensive scope offers unique insights into the potential implications of chronic cannabis use.

The research arrives as marijuana continues to grow in social acceptance as it becomes more legally available. Recreational marijuana became legal in the U.S. Virgin Islands earlier this year, and it can now be legally purchased in 23 U.S. states and all of Canada. Despite this trend, conversations about the long-term risks of cannabis use remain limited, the WSJ report noted.

The research study has been described as longitudinal, meaning it involved repeated observations of the same variables over a period of time. A longitudinal study can extend over years or even decades.

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