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Sunday is 420 day, when lovers of marijuana get together to celebrate their fondness for weed. Yet research shows that regular users of marijuana are at risk for serious conditions, including strokes, heart attacks, cardiac arrhythmias, heart failure and myocarditis, which is an inflammation of the heart muscle.
Now, an increased risk of dementia can be added to the list, according to a large study of more than 6 million people published April 14 in the journal JAMA Neurology.
“Someone who has an emergency room visit or hospitalization due to cannabis has a 23% increased risk of dementia within five years compared to someone who was at the hospital for another reason. They have a 72% greater risk compared to the general population,” said study coauthor Dr. Daniel Myran, an assistant professor in the department of family medicine at the University of Ottawa in Canada.
“Those numbers have already factored out other reasons for dementia, such as age, sex, mental health or substance use, and whether or not you have chronic conditions such as diabetes or heart disease,” Myran said.
Earlier research shows marijuana users are nearly 25% more likely to need emergency care and hospitalization than nonusers.
“However, this is not a study that anyone should look at and say, ‘Jury’s in, and cannabis use causes dementia,’” Myran said. “This is a study that brings up a concerning association that fits within a growing body of research.”
The study is a red flag for health professionals who should be screening for cannabis use disorder, said Dr. Robert Page II, a professor of clinical pharmacy and physical medicine at the University of Colorado Skaggs School of Pharmacy and Pharmaceutical Sciences in Aurora.
“People with cannabis use disorder are unable to stop using even though they encounter health or social problems from use,” said Page, who chaired the medical writing group for the American Heart Association’s 2020 scientific statement on marijuana.
“When they stop using it, they either have withdrawal symptoms or have very bad mental health symptoms,” he added. “They might have quite severe depression, or they might have anxiety, all of which can send them to the hospital.”
The potency of weed has skyrocketed over the years, which can heighten health risks and is leading to a global rise in marijuana addiction as well as cannabis use disorder, according to a 2022 study.
Addiction to marijuana can happen to about 30% of people who use cannabis, according to the US Centers for Disease Control and Prevention. The disorder also comes with a higher risk of attention, memory and learning problems, the CDC finds.
“The other takeaway from this study is that many people believe marijuana to be natural and therefore safe,” Page said. “It is a psychotropic medication, so it’s going to have psychotropic effects. If you have underlying psychiatric issues, realize that you need to be transparent with your provider and let them know if you’re using this medically or recreationally.”
Researchers looked at medical records between 2008 and 2021 for more than 6 million people between the ages of 45 and 105 without dementia who lived in Ontario. Of those, over 16,000 had been seen due to negative responses to marijuana.
“Within five years of an emergency room visit or hospitalization for cannabis, 5% of people were diagnosed with dementia, and within 10 years, 19% of people were diagnosed with dementia,” Myran said.
Rates of emergency room visits due to marijuana increased fivefold in adults between the ages of 45 and 64 and nearly 27-fold for people 65 and older during those 13 years, according to the study.
“While this study was done in Canada, it should apply to all of North America including the US,” he added, pointing to a May 2024 study that shows daily or near daily use of marijuana surpassed alcohol by 2022.
If the connection between cannabis use and dementia does turn out to be causal, just how might marijuana trigger cognitive decline in regular users? One possibility is that daily or near daily use of marijuana changes neural connectivity in the brain, Myran said.
“There’s certainly a pathway where there’s potential inflammation and microvascular damage from marijuana,” he said. “It could be that regular cannabis use causes people to develop other risk factors for dementia, such as depression, social isolation and lower educational attainment. And it could be that people who regularly use cannabis are more likely to have major trauma to the brain such as a motor vehicle collision.”
