Marijuana use is at an all-time high—Here's how it affects mental health

Marijuana use is at an all-time high in the United States. In the past decade alone, Americans' reported marijuana smoking has more than doubled, increasing from 7% to 13% from 2013 to 2023, according to a national poll from Gallup. And, a separate study found that half of adults (50%) now say they have tried marijuana at some point in their lives. 

The reported increase in marijuana use, known formally as cannabis, parallels a shift in national policy. The U.S., historically known for its racially motivated "War on Drugs," has now seen marijuana legalized for medical or recreational purposes in three-quarters (38) of all 50 states and the District of Columbia. Roughly half of those states (24) and D.C. have legalized recreational use alone for adults aged 21 and older.

Despite these shifts in reported use and policy, experts remain largely in the dark about the effects of occasional marijuana use, a result of contested federal restrictions on research. A larger body of research, though, reveals concerns about the effects of heavy, long-term marijuana use — especially on young people's mental health. 

Data shows that young people who use marijuana weekly or more double their risk of developing depression and anxiety, and cannabis use is associated with conditions like psychosis, suicide, and attention-deficit/hyperactivity disorder (ADHD) among young people.

These findings are compounded by the fact that age greatly influences the likelihood of smoking marijuana. According to Gallup's national poll, young people ages 18 to 34 are the most likely to report marijuana use of any age group surveyed — over a quarter (26%) report smoking marijuana. 

To assess how marijuana affects people's mental health, Charlie Health looked at the numbers, including data on how cannabis use is linked to psychosis, depression, and other mental health conditions. We also offer some evidence-based tips on how to cope with marijuana-related mental health issues. 

Heavy cannabis use has been linked to psychosis

Cannabis use has been linked to long-lasting psychotic disorders, with a stronger relationship seen with higher levels of use — a metric that can vary between studies but generally refers to people who use cannabis frequently and in large quantities, significantly more than occasional or moderate users. A review of 18 studies involving over 66,000 people found that heavier cannabis users had a significantly higher risk of developing psychosis. The meta-analysis showed that the heaviest users had about 3.9 times higher risk of schizophrenia and other psychosis-related outcomes compared to non-users. 

However, as mentioned above, it's important to note that multiple factors may be at play here, and the relationship between marijuana use and mental health has been found to be bi-directional. For example, data shows that rates of marijuana use are nearly twice as high among adults with a mental health condition as compared to adults without a mental health condition.

The risk of psychotic disorders is greatest among young people with cannabis dependence 

A study of nearly 7 million people looking at data between 1972 and 2021 found that cannabis use disorder (CUD) was linked to a higher risk of schizophrenia. According to the study, the risk of developing schizophrenia associated with CUD was highest among young people overall, particularly males aged 16-20. Among males aged 16-20 with CUD, the likelihood of developing schizophrenia was 3.84 (as compared to the baseline of 1.0) — more than twice the likelihood among females with CUD of the same age range (1.81). However, both of these scores still indicate that the risk of developing schizophrenia associated with CUD was highest among young people overall compared to other age groups.