A NEW study utilising functional MRI (fMRI) has found that heavy lifetime cannabis users exhibit reduced brain activity during working memory tasks, with recent users also showing similar effects. The research suggests that the impact on cognitive function could be long-lasting.
The study examined 1,003 adults aged 22 to 36 using fMRI scans. Participants completed seven cognitive tasks measuring memory, reward response, emotion, language, motor skills, and relational assessment. The findings revealed that 63% of heavy lifetime cannabis users displayed reduced brain activity during working memory tasks, while 68% of recent users also showed this decline.
“As cannabis use continues to grow globally, studying its effects on human health has become increasingly important,” said the research team in a statement. “By doing so, we can provide a well-rounded understanding of both the benefits and risks of cannabis use, empowering people to make informed decisions.”
The research team classified participants based on their cannabis use history. Heavy users had consumed cannabis more than 1,000 times, moderate users between 10 and 999 times, and non-users fewer than 10 times. Of the study cohort, 8.8% were heavy users, 17.8% moderate, and 73.4% non-users.
Brain regions affected by heavy cannabis use included the anterior insula, medial prefrontal cortex, and dorsolateral prefrontal cortex—areas crucial for decision-making, memory, attention, and emotional processing. The study found that heavy users had significantly lower activation in these regions, with a Cohen d value of -0.28, indicating a notable difference from non-users.
Despite these findings, researchers stress the need for further studies. “There are a lot of questions we still need answers to regarding how cannabis impacts the brain,” the team noted. “Large, long-term studies are needed to understand whether cannabis use directly changes brain function, how long these effects last, and the impact on different age groups.”
As cannabis legalisation expands globally, this research highlights the importance of understanding its cognitive effects, particularly on working memory, which is essential for daily functioning.
Reference
Gowin JL et al. Brain function outcomes of recent and lifetime cannabis use. JAMA Netw Open. 2025;8(1):e2457069.
