A major Canadian study has found that people who end up in the ER due to cannabis use face a significantly higher risk of developing dementia. The findings raise new concerns about the health effects of high-strength marijuana, particularly among older adults.
Key Facts: dementia risk factor linked to emergency cannabis use
- A study in JAMA Neurology found a 23% higher risk of dementia in cannabis users who visited the ER.
- Hospitalized cannabis users faced a 72% greater dementia risk within five years.
- Data came from over 6 million adults in Ontario, Canada, from 2008 to 2021.
- The highest increase in ER visits for cannabis use was seen in adults over 65, with a 27-fold jump.
- Researchers warned that the study shows an association, not proof that cannabis causes dementia.
The Rest of the Story: Cannabis and dementia risk factor study results
The Institute for Clinical Evaluative Sciences (ICES) analyzed data from 6.9 million adults aged 45 and up across Ontario.
Among them, 16,275 individuals received emergency or hospital care tied to cannabis use.
The study found these individuals were more likely to be diagnosed with dementia in the following five years.
Lead researcher Dr. Daniel Myran clarified the study does not prove cannabis causes dementia.
However, the correlation persisted even when controlling for other health and socioeconomic factors.
Older adults experienced the steepest rise in emergency care related to marijuana, increasing from 353 cases in 2008 to 2,508 in 2021.
The dementia diagnosis rate was also striking: 5% of older cannabis-related ER patients were diagnosed with dementia within five years, and 19% within ten.
The researchers noted the study only looked at a high-risk subgroup—those whose marijuana use led to acute care.
"Risk of Dementia in Individuals With Emergency Department Visits or Hospitalizations Due to Cannabis"
Causality vs. Correlation: The study shows an association between cannabis-related acute care and dementia but cannot establish causation. Unmeasured factors (e.g., lifestyle,… pic.twitter.com/Mn8evE7iwE
— Marc Landers (@marclanders) April 15, 2025
Commentary: Time to examine high-potency cannabis as a dementia risk factor
While legalization has mostly worked as intended, the issue here isn’t cannabis in general—it’s the extreme potency of modern products, especially vapes.
These are not your granddad’s joints.
THC levels in some vape products reach 80% or more, far higher than what existed just a decade ago.
When older adults or those with underlying health issues consume ultra-high-potency marijuana, the body and brain may not handle it well.
The dramatic rise in hospital visits among adults over 65 should be a wake-up call.
It shows that what’s legal isn’t always safe.
We support legal access to cannabis, but it’s time to ask hard questions about these concentrated forms.
Should vape pens packed with extreme THC be sold as casually as a six-pack?
Or should they face additional regulations, just like hard liquor does compared to beer?
This isn’t about rolling back legalization—it’s about making it smarter.
When emergency rooms are seeing five to 27 times more cases tied to marijuana over a decade, that’s a public health flag.
The research is careful not to assign blame, but even a strong association should make policymakers pause.
Older Americans deserve clear warnings and safe products—not a free-for-all market that assumes every user is 25 and healthy.
The Bottom Line: Dementia risk factor may rise with high-potency cannabis
A large Canadian study found that older adults who had emergency visits tied to cannabis use faced a significantly higher risk of developing dementia.
The concern isn’t casual use but what happens when extremely high-THC products are involved.
Legal marijuana may be here to stay, but that doesn’t mean every version of it is without serious risk—especially for vulnerable populations.
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