Heavy Cannabis Use May Alter Brain Activity

TOPLINE:

Heavy lifetime cannabis use is linked to reduced brain activation during working memory tasks in young adults, while recent use is also associated with reduced activation during cognitive tasks, new research shows.

METHODOLOGY:

• Researchers analyzed data collected between 2012 and 2015 from the Human Connectome Project.
• The cross-sectional study included more than 1000 young adults aged 22-36 years (mean age, 29 years; 53% women; 76% White individuals)
• Participants were categorized as heavy cannabis users (≥ 1000 lifetime uses; 9%), moderate users (11-999 lifetime uses; 18%), or nonusers (≤ 10 lifetime uses; 73%). Recent use was determined using urine toxicology screening.
• Participants underwent MRI while performing seven cognitive tasks assessing working memory; reward, emotion, and language processing; motor function; relational assessment; and theory of mind.

TAKEAWAY:

• Heavy lifetime cannabis use was associated with significantly lower activation on the working memory task (Cohen d, −0.28; false discovery rate corrected P = .02).
• Reduced activation in heavy cannabis users was observed in the anterior insula, medial prefrontal cortex, and dorsolateral prefrontal cortex.
• Recent cannabis use was also associated with lower brain activation during working memory tasks, as well as motor tasks; but this did not remain significant after false discovery rate correction.
• The association between heavy lifetime cannabis use and reduced brain activation during the working memory task persisted even after excluding participants with recent cannabis use.

IN PRACTICE:

“Evidence supported that both recent and heavy cannabis use were associated with diminished brain activation,” the investigators wrote, adding that abstaining before doing a cognitive take may help improve performance.

“People need to be aware of their relationship with cannabis since abstaining cold turkey could disrupt their cognition as well. For example, heavy users may need to be more cautious,” study lead author Joshua Gowin, PhD, Department of Psychiatry, University of Colorado Anschutz Medical Campus, Aurora, Colorado, said in a press release.

SOURCE:

The study was published online on January 28 in JAMA Network Open.

LIMITATIONS:

The cross-sectional design of the study prevented the establishment of causal relationships. The findings may not generalize beyond the young adult population included. The researchers lacked data on tetrahydrocannabinol dose, potency, additional cannabis constituents, and route of administration. In addition, the timing of recent cannabis use relative to scanning was unknown, potentially affecting the magnitude of observed associations. Some subgroups were also small, limiting statistical power, and the study could not examine the use of other substances or psychiatric comorbidities.

DISCLOSURES:

The study was supported by the National Institute of Mental Health (NIH), 16 NIH institutes and centers, the McDonnell Center for Systems Neuroscience at Washington University, and the National Institute on Drug Abuse. One investigator received NIH grants during the study, and another received grants from multiple health organizations, travel support, and speaker honorarium. Details are fully listed in the original article.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.