A new study out of Canada, one of the first countries to legalize marijuana use in 2018, indicates an alarming increase in mortality for persons with cannabis use disorder (CUD). For this study, CUD was defined as hospital-based treatment, including emergency room treatment and/or hospitalization.

The study involves dozens of international researchers under the leadership of Dr. Daniel T. Myran, Canada Research Chair at the University of Ottawa, and a huge data set: 11.6 million Canadians, ages 15 to 105, tracked for a median of five years. Initially, they found that the rate of death in the next five years for people with CUD is six times the average rate:

Within 5 years of care for CUD, 3770 individuals (3.5%) died compared with 2550 members (0.6%) of the matched general population.

Once that number was adjusted for comorbid substance use disorders and mental health disorders, it still came in at 2.8 times the average rate. Researchers note that other substance use disorders have a higher five-year mortality rate than CUD:

Individuals with hospital-based CUD care had a slightly lower risk of death within 5 years than individuals with alcohol use disorder and about half the risk of death of individuals with hospital-based care for stimulants or opioids.

And researchers point out that cannabis use was not listed as the cause of a single death. Treatment for CUD, however, was correlated with much higher rates of death from all causes in the next five years. In particular, it is associated with a tenfold increase in suicide rates and a fivefold increase in deaths by trauma (car accident, drowning, falls, and other accidents). Here are some of the other results:

Individuals with hospital-based CUD care were more likely to have had an [emergency room] visit or hospitalization for substance use (38.9% vs 1.7%) or a mental disorder (34.8% vs 3.0%) in the past 3 years along with an outpatient mental health or addiction visit (68.2% vs 26.1%) relative to the general population. 

Individuals with hospital-based CUD care were more likely to have been diagnosed with several chronic conditions including hypertension (8.0% vs 6.6%), asthma (25.9% vs 18.7%), COPD (1.6% vs 0.4%), cardiovascular disease (1.1% vs 0.6%), and kidney failure (2.1% vs 0.6%) compared with the general population with no difference in prior cancer diagnoses (13.5% vs 13.1%).

Researchers are sounding the alarm about the relationship between THC and mortality. Dr. Myran told UPI, “Large segments of the public do not perceive cannabis to have major health risks.” The researchers note that cannabis use is surging; it is now more widely used in Canada than alcohol. 

Now we know you’re five times more likely to die from an accident and 10 times more likely to die by suicide if you have been treated for CUD. That’s something to consider when crafting public policy around marijuana use.

Written by Steve O’Keefe. First published February 12, 2025.

Sources:

“Cannabis Use Disorder Emergency Department Visits and Hospitalizations and 5-Year Mortality,” JAMA Network, February 6, 2025.

“Marijuana addiction increases risk for premature death, Canadian study finds,” UPI, February 6, 2025.

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