Cannabis may be legal in more places and socially accepted than ever—but a new study out of Arizona suggests it’s sending more people to the hospital, and mental health is often the reason why.
Published in the Journal of Studies on Alcohol and Drugs, the study found that cannabis-related hospital visits increased by 20% across Arizona between 2016 and 2021. And in about one in four of those visits, a mental health condition like bipolar disorder, depression, or psychosis was the primary diagnosis. That compares with just 3% of hospital visits unrelated to cannabis.
“Overall, people with a cannabis-related hospital visit were nearly eight times as likely to have a primary diagnosis of a mental health disorder,” said lead researcher Madeline Meier.
Even more concerning: the connection between cannabis and mental health hospitalizations grew stronger over the five-year study period.
“I think it’s important for people to be aware that the science on using cannabis to treat mental health problems is really not there yet,” said Meier.“In fact, there is evidence suggesting that cannabis use can worsen mental health conditions, or even increase the risk of developing them.”
One of the study’s more surprising findings: Adults over 65 had the largest increase in cannabis-related hospital visits—especially those linked to mental health.
This study highlights a public health blind spot: as cannabis becomes more accessible, public education has continued to lag and false information runs rampant, especially around its potential mental health risks.
After all, if one in four cannabis-related ER trips ends with a psych diagnosis, it might be time to start treating cannabis not just as a product, but as a substance that deserves clear-headed, evidence-based guidance as it is most likely not as safe as people claim.
MH Meier et al, Trends in Cannabis-related Hospitalizations in Arizona from 2016-2021 and Associations with Mental Health-related Hospitalizations. Journal of Studies on Alcohol and Drugs (2025). DOI: 10.15288/jsad.23-00379
