In the United States, cannabis — AKA marijuana — is available recreationally in 22 states and Washington, D.C. While marijuana has always been a popular choice among young adults, new data shows the drug may contribute to mental health risks.
A study published in Psychological Medicine finds that young men with cannabis use disorder are more likely to develop schizophrenia. The research included investigators from the University of Copenhagen and the U.S. National Institute of Health’s (NIH) National Institute on Drug Abuse (NIDA).
According to the NIH, marijuana’s popularity with young adult crowds is at an all-time high. Young adults between the ages of 19 to 30 years old who reported marijuana use in 2021 reached 43%, versus 34% in 2016. Daily marijuana use is also on the rise, 11% of young adults reported daily use in 2021, nearly a two-fold increase from 6% in 2011.
Researchers from Denmark and the NIDA analyzed over six million health records of Danish health records spanning nearly 50 years (1971 to 2021). Investigators examined the incidence of schizophrenia cases due to cannabis use disorder. Their findings produce a strong link between cannabis use disorder in young men.
NIDA Director and study co-author Nora Volkow, M.D., explains the importance of their discoveries in an NIH news release. "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.”
In their results, researchers estimate 15% of schizophrenia cases for men 16 to 49 years old could have been avoided by preventing cannabis use disorder. For young men between the ages of 21 to 30 years old, 25% to 30% of schizophrenia cases could have been dodged by slowing down marijuana use. Women are less susceptible to schizophrenia caused by cannabis use disorder. Cannabis use disorder was responsible for only 4% of schizophrenia cases in women aged 16 to 49.
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. This study adds to our growing understanding that cannabis use is not harmless, and that risks are not fixed at one point in time.– Lead author and associate professor at the University of Copenhagen, Carsten Hjorthøj, Ph.D.
What is cannabis use disorder?
Cannabis use disorder occurs when a marijuana user is unable to stop using the drug, even if it is causing health or social issues. According to the CDC, around three in 10 people who use marijuana suffer from cannabis use disorder.
The CDC notes cannabis use disorder may arise from greater amounts of THC (delta-9-THC). Over the years, the amount of THC in marijuana has increased substantially. The average THC concentration has risen from 9% in 2008 to 17% in 2017. Delta-8 THC is becoming a popular substitute for delta-9-THC to receive similar effects in states where marijuana is illegal. However, much is still unknown about delta-8-THC as it is currently not approved by the FDA.
Volkow says, "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."