Marijuana Dependence Linked to Increased Mortality and Psychosis Risks, New Studies Show

Two recent studies from Canada have highlighted concerning health risks associated with cannabis use disorder (CUD), shedding light on higher death rates and a rise in psychosis and schizophrenia cases linked to marijuana dependency, the New York Times reports.

The first study, published on Thursday, is the largest to date examining death rates among individuals diagnosed with CUD. The findings indicate that patients with cannabis use disorder, defined as the inability to stop using marijuana despite negative consequences, died at nearly three times the rate of individuals without the disorder over a five-year period. Those with CUD were found to be 10 times more likely to die by suicide compared to the general population, and they also had higher rates of death due to trauma, drug poisonings, and lung cancer. The researchers noted that these figures suggest CUD presents risks that are roughly half as severe as opioid addiction and slightly less dangerous than alcohol use disorder.

The study utilized health records from Ontario, which tracks the healthcare interactions of nearly the entire population. The researchers identified 106,994 individuals diagnosed with CUD between 2006 and 2021 and found that 3.5% of them died within five years of treatment for the disorder, compared to just 0.6% of a matched control group. After accounting for other contributing factors such as mental health disorders and substance use, the study concluded that individuals with CUD faced a 2.8 times greater risk of death. This risk was particularly pronounced among young adults aged 25 to 44.

Dr. Daniel Myran, the study’s lead author, cautioned that these figures might underestimate the full extent of cannabis’s impact.

“For every person treated for CUD, there are likely three others who did not seek care,” he said.

While the study could not conclusively determine whether cannabis itself was the direct cause of increased mortality, Dr. Myran emphasized that the group of individuals diagnosed with CUD is clearly at high risk, suggesting the need for early intervention and preventive measures.

In a second report published earlier this week, the same research team analyzed the rise of cannabis-related psychosis and schizophrenia in Canada following the legalization of marijuana. Cannabis has long been linked to the development of these mental health conditions, and the new study found a noticeable increase in cases attributed to cannabis use disorder since the country’s move to legalize recreational marijuana.

The study compared rates of psychosis and schizophrenia across three distinct periods: before legalization (2006-2015), during the period of expanding medical and non-medical cannabis use (2015-2018), and after recreational cannabis was legalized (2018-2022). The results revealed that while schizophrenia rates remained stable, the proportion of schizophrenia cases linked to cannabis use disorder rose sharply from 3.7% before legalization to 10.3% after. Additionally, the rate of psychosis cases nearly doubled following legalization.

Young adults aged 19 to 24 were found to be the most vulnerable to these effects. According to Dr. Jodi Gilman, an associate professor of psychiatry at Harvard Medical School, this age group is particularly susceptible due to ongoing brain development and the fact that psychosis and schizophrenia often emerge in young adulthood.

“This is a period of the lifespan when the brain is still developing and vulnerable to cannabis’s effects,” Dr. Gilman explained.