• Posted April 16, 2025

Heavy Weed Use Increases Risk Of Dementia

Middle-aged folks and seniors whose weed use lands them in the hospital are at higher risk for developing dementia within a matter of years, a new study says.

An ER visit or hospitalization due to cannabis use is associated with a 72% increased risk of a dementia diagnosis within five years compared to the general population, researchers reported April 14 in JAMA Neurology.

These folks also have a 23% increased risk of dementia within five years compared to people receiving hospital care for any other reason, researchers added.

“Long-term and heavy cannabis use has been associated with memory problems in midlife along with changes in brain structure associated with dementia,” said lead investigator Dr. Daniel Myran, research chair in social accountability at the University of Ottawa in Canada.

“We set out to estimate the risk of being diagnosed with dementia in a group of people whose cannabis use resulted in a visit to the emergency room or required a hospitalization for treatment,” he added in a news release.

Researchers tracked 6 million people 45 and older from Ontario who had no history of dementia when they joined the study.

Between 2008 and 2021, more than 16,000 of them required hospital care due to weed use, researchers said.

The annual rate of first-time hospital visits for weed use increased more than five-fold during the study, rising from about 7 people for every 100,000 in 2008 to nearly 38 per 100,000 in 2021.

About 5% of those in the hospital for weed use developed dementia within five years, and 19% did so within 10 years, researchers said.

By comparison, under 4% those at the hospital for other health problems developed dementia within five years and 15% within 10 years.

In the general population, a little over 1% of folks had dementia diagnosis within five years, and nearly 6% within 10 years, results show.

Overall, the risk of dementia associated with a hospital visit for weed use was slightly lower than the risk associated with a hospital care for alcohol use, researchers said.

There are a couple of reasons why weed use might make a person prone to dementia, researchers said.

“Regular cannabis use might directly increase the risk of dementia through changes in brain structure,” senior researcher Colleen Webber, a scientist at the Bruyère Health Research Institute in Ottawa, said in a news release.

“It’s also possible that regular cannabis use increases the risk of other established risk factors for dementia, including high blood pressure, head trauma and other injuries, and a higher risk for depression and social isolation,” she added.

However, researchers noted that this study could not draw a direct cause-and-effect link between weed use and dementia.

"While we collectively need more research to better understand potential risks of regular cannabis use on cognition and dementia, we hope these findings can inform discussion between patients and healthcare providers,” Myran said.

More information

Harvard Medical School has more on the long-term cognitive effects of weed use.

SOURCE: Institute for Clinical Evaluative Sciences, news release, April 14, 2025