Emergency Care for Cannabis Use Associated with Increased Risk for Dementia in Adults: Canadian Population Study
Adults with a cannabis-related acute care visit or hospitalization were at 23% and 72% greater risk of a new dementia diagnosis within 5 years, a new study finds.
Adults who sought emergency medical care for cannabis-related issues were significantly more likely to be diagnosed with dementia within 5 years, according to a large Ontario-based cohort study published in JAMA Neurology.
After multivariable adjustment for sociodemographic factors and chronic health conditions, researchers found that individuals aged 45 and older who had an emergency department (ED) visit or hospitalization due to cannabis use remained at a 23% (adjusted HR, 1.23, 95% CI, 1.09-1.39) greater risk of a new dementia diagnosis compared to those with acute care for any other cause, and at 72% (aHR 1.72, 95% CI 1.38-2.15) greater risk compared to the general population.
Findings of the study, led by Daniel Myran, MD, MPH, senior author and Canada Research Chair in Social Accountability at the University of Ottawa, are based on data from 6 million adults in Ontario, Canada, who were dementia-free at baseline and followed between 2008 and 2022. Among these, 16,275 (0.3%) had a cannabis-related acute care visit. Among individuals aged 45 to 64, the annual rate of such visits increased more than 5-fold over the study period, from 6.9 per 100,000 individuals in 2008 to 37.6 per 100,000 in 2021. Among individuals aged 65 and older, the increase was even more striking—rising 26.7-fold (from 0.65 to 16.99 per 100,000).
The group of individuals who received incident acute care had a mean age of 55.2 years, and more than half (60.3%) were men. The majority (76.4%) received care in the ED, while 23.6% were treated as inpatient.
“Regular cannabis use might directly increase the risk of dementia through changes in brain structure,” study co-author Colleen Webber, PhD, MSc, said in a statement. “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.”
Myran, Webber and colleagues found that 5% of adults with cannabis-related acute care were diagnosed with dementia within 5 years, and 19% within 10 years. In contrast, the 5- and 10-year dementia rates were 3.6% and 14.8%, respectively, among those with acute care for other reasons, and 1.3% and 5.5% in the general population. The risk remained elevated but was moderately lower than that observed in individuals who received acute care for alcohol use.
The retrospective population-based study matched 15,120 adults with cannabis-related acute care with 125,704 with all-cause acute care. The primary outcome, a diagnosis of dementia, including Alzheimer disease, was identified using validated assessment tools and ICD-10 coding.
The findings are of particular concern given an observed trend in greater cannabis use among older individuals. According to recent research, 1 in 8 older adults use cannabis products, and the proportion has increased since before the COVID-19 pandemic. The study found that 12% of older Americans say they have consumed a THC-containing substance in the past year and 4% saying they do so multiple times a week. The study was conducted among adults aged 50 to 80 years.3
The authors noted the dearth of research about the epidemiologic links between use of cannabis and dementia and the inconsistent results reported. "Adding to the literature, we present the largest study to date, to our knowledge, on the longitudinal association between cannabis use leading to an ED visit or hospitalization and dementia diagnosis," they wrote.
They also observed increases in incidence of cannabis-related acute care among older adults over time, most occurring after Canada’s liberalization of medical cannabis in 2014 and the government’s “commitment to legalization of nonmedical cannabis in December 2015.”
Among the study’s limitations, Myran et al note the inability to examine patterns of use cannabis use that did not require acute care. Also, while the study demonstrates a strong association, it does not establish causation
“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 added.
