Middle-aged and elderly people who sought hospital or emergency room care for cannabis use were nearly twice as likely to develop dementia over the next five years compared to similar people in the general population, a large Canadian study reported Monday.
A study found that the risk of developing dementia was 23% higher among cannabis users when compared to adults who sought care for other reasons, the study said.
The study included medical records of six million Ontario from 2008 to 2021. The authors described health and sociodemographic differences between comparative groups.
This data does not reveal how much cannabis was used by subjects, and this study does not demonstrate that regular or heavy cannabis use plays a causal role in dementia.
However, the finding raises serious concerns that require further exploration, said Dr. Daniel T. Myran, the first author of the study published in Jama Neurology.
“Knowing whether it can cause cannabis use or severe, regular chronic use is a challenging and complicated question that causes dementia is not answered in one study,” says Dr. Milan, an assistant professor of family medicine at the University of Ottawa.
“This contributes to the literature and signs or signals of concern.”
Myran's previous study found that patients with cannabis use disorder died almost three times more than undisabled individuals over five years. He also reports that more cases of schizophrenia and psychosis in Canada have been linked to cannabis use disorder since the drug was legalized.
Latest research focusing on dementia adds a lot of literature on regular or heavy cannabis use and cognition. Researchers report the effects of verbal learning, memory and attention, while imaging studies point to brain changes associated with the use of cannabis and other substances.
Veterans with traumatic brain damage in addition to cannabis use disorders could be at increased risk for early-onset dementia, researchers reported last year.
However, much of the research is relatively small. The strength of the new report is its large sample, and its ability to track patients who were not diagnosed with dementia when they participated in the study over a long period of time, said Madeline Meyer, an associate professor of psychology at Arizona State University, who was not involved in the study.
“They were able to rule out dementia during their first cannabis visit and show temporary order. Cannabis came first and dementia became second,” Dr. Meyer said.
Her research has been tested regularly following a cohort of over 1,000 individuals over the years, linking cannabis use with neuropsychological decline.
“I want to fight against this whole idea that cannabis is harmless and perhaps even has some medical benefits,” Dr. Meyer said. “This study shows an association that people think should take seriously and say, 'This may be putting me at risk.' ”
She noted that a study by Dr. Mylan and his colleagues found that people seeking care for alcohol use are more likely to be diagnosed with dementia than cannabis users.
“I'm worried about that baby boomer drug abuse,” she said.
More and more people, including seniors, are using cannabis. Cannabis-related medical visits increased more than five times between 2008 and 2021, among adults aged 45 and older, a new study found. Visits increased almost 27 times among adults over the age of 65.
The study included more than 6 million people aged 45 and older who had not had a diagnosis of dementia at the start of the study. Of these, 16,275 people had acute care medical encounters due to cannabis.
Patients with cannabis-related visits were compared to the general population that matched the 140,824 matched patients who needed medical care for all other reasons.
Within five years, 5% of people who visited acute cannabis were diagnosed with dementia. The figure for individuals who needed care for other reasons was 3.6%, while the figure for similar individuals in the general population was 1.3%.
However, people who are heavy cannabis users are unlike those who are not in different ways, and some of them may help explain the increased risk of dementia, explained Dr. Milan.
Some factors can be explained, but he said, “You can't control them all.”
Another unknown, he said, was self-control. Those who have begun to experience symptoms of cognitive decline may be more likely to turn to cannabis. If so, “cannabis looks like it's causing dementia, but it's on the pathway – they already had dementia,” Dr. Milan said.
After adjusting for other factors including age, gender, income and other health conditions, he and his colleagues determined that patients seeking care for cannabis-related reasons were 1.23 times more acute care than patients diagnosed with dementia and 1.72 times more than patients in the healthier general population.
