Your brain may not bounce back as quickly as you think after you smoke weed.
A groundbreaking new study suggests that heavy marijuana use could leave lasting marks on your memory, long after your last hit.
The study, conducted by researchers at the University of Colorado School of Medicine, was published in JAMA Network Open on Tuesday.
The study
It’s the largest study of its kind to ever be completed – examining the effects of cannabis use on over 1,000 young adults aged 22 to 36 using brain imaging technology.
The researchers then studied the neural response of participants during a magnetic resonance imaging (MRI) session and gave them seven cognitive tasks to complete.
The tasks tested working memory, reward, emotion, language, and motor skills – such as tapping a finger to map brain control, relational assessment, and theory of mind.
Participants were categorized into three groups based on their lifetime use of the drug:
- Heavy users (more than 1,000 times)
- Moderate users (10-999 times)
- Non-users (fewer than 10 times)
The findings
The researchers found that 63% of heavy lifetime cannabis users exhibited reduced brain activity during a working memory task, while 68% of recent users also demonstrated a similar impact.
Heavy users—who made up about 9% of participants—exhibited lower brain activity during memory tasks than those who rarely or never used cannabis. The biggest differences appeared in brain regions responsible for attention, decision-making, and short-term information storage.
“We applied the highest standards to our research, setting rigorous thresholds for statistical significance across all seven cognitive function tests. To minimize the risk of false positives, we employed false discovery rate (FDR) correction. While some of the other tasks indicated potential cognitive impairment, only the working memory task showed a statistically significant impact,” said the study’s first author Joshua Gowin, PhD, assistant professor of radiology at the University of Colorado School of Medicine.
KIRO 7′s Gwen Baumgardner is taking a closer look at the findings of this study and will have a full report tonight at 6 p.m.
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