Long-Term Medical Cannabis Use Has No Significant Harmful Effects On Memory Or Impulse Control, New Study Says

A new study published in JAMA Network Open provides a comprehensive look into the effects of year-long medical cannabis use on brain function, with surprising results. Despite the growing popularity of cannabis as a treatment for symptoms like depression, anxiety, pain and insomnia, the study found no significant changes in brain activity linked to cognitive functions after a year of use.

The research, led by Debbie C. L. Burdinski, BS, and a team of experts, explored the neural implications of cannabis use in 57 adults who had newly obtained medical cannabis cards (MCC) for symptom relief. Conducted over three years from 2017 to 2020 in the greater Boston area, the study aimed to examine whether regular cannabis use affected cognitive processes such as working memory, reward processing and inhibitory control, key areas that are often believed to be impacted by cannabis use.

Key Findings From Brain Imaging

Participants underwent functional magnetic resonance imaging scans at the beginning of the study and again one year later to assess brain activity during tasks requiring memory, impulse control and decision-making. These imaging results were then compared with a control group that did not use cannabis.

Surprisingly, the study reported no “statistically significant difference in brain activation between the two time points” in the medical cannabis group. There was also no link between the frequency of cannabis use and changes in brain activity after one year. The findings challenge some earlier research that suggested prolonged cannabis use might alter brain function, particularly in areas tied to executive functioning.

The study’s authors note that this research is unique because it examines longitudinal changes in adults who began using cannabis for medical reasons, as opposed to recreational use. "Cannabis is increasingly being used to treat medical symptoms, but the effects on brain function in those using cannabis for these symptoms are not known," the report states.

A Closer Look At Cognitive Domains

The study tested three key cognitive areas: working memory, reward processing and inhibitory control. These functions are often thought to be influenced by cannabis, particularly in recreational users who consume high doses. However, this new research suggests that moderate cannabis use for medical purposes may not significantly impair these functions.

During the study, participants performed tasks designed to measure their memory, ability to process rewards and control impulses. Despite increases in cannabis use over the year, the study revealed that “functional imaging measures during working memory, reward and inhibitory control tasks did not differ statistically from baseline to one year.”

This was a significant finding because earlier research has suggested cannabis could impair these cognitive abilities. But, the results of this study indicate that, at least for moderate users seeking symptom relief, those fears may be unfounded.

Implications For Medical Cannabis Users

With the medical cannabis industry growing rapidly—especially in the U.S., where 38 states and Washington D.C. now have medical cannabis programs—this study offers valuable insight. As more adults turn to cannabis for relief from chronic pain, anxiety and other conditions, understanding the potential long-term effects on the brain is crucial.

However, the study's authors caution that more research is needed, particularly involving younger populations and higher doses of cannabis. The study participants were predominantly older, well-educated adults, a demographic that might not be representative of the broader medical cannabis user base. Furthermore, medical users may have different consumption patterns than recreational users, making it difficult to generalize findings.

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