A major new study published in JAMA Neurology has found that regular marijuana use may significantly increase the risk of developing dementia, raising new concerns about the long-term effects of cannabis on brain health.
Researchers analyzed data from over 6 million people in Ontario, Canada, between 2008 and 2021. The findings showed that individuals who were hospitalized or visited the emergency room for cannabis-related issues had a 23% higher risk of developing dementia within five years compared to those hospitalized for unrelated reasons, and a 72% greater risk compared to the general population.
Crucially, this elevated risk remained even after adjusting for common dementia risk factors such as age, sex, mental health conditions, chronic illnesses, and other substance use.
The study’s authors emphasize that this should serve as a “red flag” for healthcare professionals, urging increased screening for cannabis use disorder (CUD) — a condition marked by the inability to stop using marijuana despite negative impacts on health or social life. Those with CUD often experience withdrawal symptoms, depression, and anxiety when they try to quit.
As marijuana becomes more widely used and accepted, experts are sounding the alarm about its dramatically increased potency over the past two decades. This higher potency is believed to be driving a global increase in addiction rates and cannabis use disorder. Research suggests that around 30% of marijuana users may develop some form of addiction, which has been associated with memory, attention, and learning deficits.
Many people falsely assume that marijuana is “natural” and therefore harmless. But researchers stress that marijuana is a psychotropic substance, capable of altering mood, perception, and cognitive function — and potentially triggering long-term brain changes.
Among the most alarming statistics in the study: Within five years of a cannabis-related ER visit or hospitalization, 5% of individuals were diagnosed with dementia, and that number rose to 19% within 10 years. During the same study period, emergency room visits linked to marijuana use increased fivefold for adults aged 45 to 64, and nearly 27-fold for those aged 65 and older.
Experts believe several mechanisms may explain marijuana’s link to cognitive decline, including:
- Disruption of neural connectivity
- Inflammation and microvascular damage in the brain
- Increased vulnerability to other dementia risk factors, such as depression, social isolation, lower educational attainment, and brain trauma
As marijuana use continues to rise, particularly among older adults, this study underscores the need for greater public awareness, better education about the risks, and more robust screening tools in clinical settings.
https://www.cnn.com/2025/04/20/health/marijuana-dementia-wellness