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Does Marijuana Use Increase the Risk of Mental Illness in Young Adults?

Two new studies link the use of marijuana among teens and young adults to an increased risk of mental illness. If true, this is especially concerning given the trend towards legalization of recreational marijuana use across the country.

Cannabis Use Disorder Linked to Schizophrenia

The first study, from researchers in Denmark in collaboration with the United States National Institutes of Health, found a link between Cannabis Use Disorder and schizophrenia. (Cannabis Use Disorder, also called Marijuana Use Disorder, is defined as the continued use of cannabis despite impairment in psychological, physical, or social functioning.) This link was most striking in young adults aged 21 to 30 and affected males more than females.

The Danish research, published in the journal Psychological Medicine, studied almost 7 million individuals between the ages of 16 and 49. The research took place over the course of several decades, from 1972 to 2021.

The study’s researchers concluded that the chemical THC found in marijuana may trigger or worsen schizophrenia among susceptible individuals. This is especially so in individuals with regular high THC intake or diagnosed cannabis use disorder.

Teenagers Who Use Cannabis More Likely to Develop Psychiatric Disorders

Another recent study further links marijuana use to the risk of mental illness. This study, from researchers at Columbia University, found that teenagers who use cannabis recreationally are 2 to 4 times more likely to develop psychiatric disorders than those who don’t use cannabis at all. The study found increased incidence of depression, suicidal ideation, slower thoughts, difficulty concentrating, and aggression.

The Columbia University survey analyzed the behavior of more than 68,000 adolescents aged 12 to 17, from 2015 to 2017. Unlike the Danish research, this study focused on recreational cannabis use rather than the heavier use characteristic of Cannabis Use Disorder.

Is There Causality?

The correlation between marijuana use and psychiatric disorders is controversial. Some experts point out that since both surveys were observational, they do not directly prove cause and effect. As such, it’s unclear whether individuals who already have or are developing psychiatric conditions are more likely to turn to cannabis to self-medicate or whether cannabis use triggers mental problems.

That said, the two studies taken together suggest that the risks of marijuana use are real. This is especially so given the increase in recreational marijuana use among young adults due to the legalization of the drug in 22 states, including Minnesota.

How Does Cannabis Affect the Developing Brain?

Multiple studies beyond these two suggest that marijuana use by teenagers has adverse effects on developing brains. Marijuana use can affect teens’ attention, memory, and learning.

The brain is one of the last human organs to fully develop, not finishing until the mid-to-late 20s. This makes adolescents and young adult particularly vulnerable to the effects of cannabis as their brains mature.

Experts believe that THC, the chemical found in cannabis, affects the endocannabinoid system. This is a complex signaling system in the brain that plays an important role in sculpting the brain during adolescence, when schizophrenia typically manifests itself. Disturbing that system could have a significant impact on brain development.

How Valley Medical is Fighting Cannabis Abuse

While marijuana is commonly used as a recreational drug (and increasingly being legalized by many states, including Minnesota), many people who use marijuana develop Cannabis Use Disorder. Studies estimate that between 10% and 30% of marijuana users become addicted to the drug.

Valley Medical and Wellness offers treatment for Cannabis Use Disorder alongside its treatment for other abusive substances. To treat Cannabis Use Disorder, Valley Medical recommends the use of Naltrexone and other medication-assisted treatments in conjunction with cognitive behavioral therapy.

Let the Addiction Treatment Experts at Valley Medical and Wellness Help Manage Your Cannabis Abuse

If you or a loved one is suffering from Cannabis Abuse Disorder, the addiction treatment experts at Valley medical can help. We have clinics in five convenient locations to serve patients across Minnesota, including Burnsville, Minneapolis, Woodbury, Rochester, and Bemidji. To learn more, call us at (612) 444-3000.

For more information about our services and to keep up with the latest events happening at the clinic, check us out on:


Michael Miller Michael Miller Michael Miller is a Business Process Writer at Valley Medical and Wellness. He's an established writer with more than 200 books and thousands of articles published over the past three decades. He writes on a variety of topics, from healthcare to technology to music. He is also a member of the Interstellar Foundation, dedicated to telling the story of humankind via NASA spacecraft traveling beyond the solar system.

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