Cannabis Use Linked With Diminished Brain Activation in Young Adults
A lifetime history of heavy cannabis use in young adults was associated with lower brain activation during a working memory task, according to a study in JAMA Network Open. The association remained after researchers excluded participants with recent cannabis use.
“These findings identify negative outcomes associated with heavy lifetime cannabis use and working memory in healthy young adults that may be long lasting,” wrote corresponding author Joshua L. Gowin, PhD, of the University of Colorado Anschutz Medical Campus, Aurora, Colorado, and study coauthors.
The study included 1003 US adults whose average age was 28.7. Among them, 8.8% had more than 1000 uses and were thus categorized as heavy cannabis users, 17.8% had between 10 and 999 uses and were considered moderate users, and 73.4% had fewer than 10 uses and were deemed nonusers.
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During functional magnetic resonance imaging sessions, researchers assessed brain activation during tasks involving working memory, reward, emotion, language, motor, relational assessment, and theory of mind. On the day of scanning, participants provided urine samples to check for recent cannabis use.
Heavy lifetime cannabis use was associated with lower brain activation on the working memory task, according to the study, even after individuals with recent use were removed. In heavy cannabis users, lower brain activation during the working memory task was most pronounced in the dorsolateral prefrontal cortex, medial prefrontal cortex, and anterior insula.
Analysis initially linked recent cannabis use with lower brain activation during working memory and motor tasks. However, the association did not survive false discovery rate correction. No other tasks were associated with heavy lifetime use, recent use, or a diagnosis of cannabis dependence, researchers reported.
“Evidence supported that both recent and heavy lifetime cannabis use were associated with diminished brain activation and cognitive performance during working memory,” the authors wrote. “These findings suggest that large, longitudinal studies are needed to assess the causality of cannabis use toward altering brain function and the duration over which these effects persist.”
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