MRI shows 'long-lasting' impact of cannabis use on brain regions linked to memory
New research is sounding the alarm on cannabis use and its impact on neural health, revealing that its routine consumption can alter the long-term function of brain regions associated with memory.
These effects are most notable in heavy lifetime users, even if they have abstained from cannabis use for prolonged periods. The findings should serve as a warning that cannabis, which is often touted as a safer and more natural alternative to alcohol, can cause harm, authors of the new JAMA paper caution.
“Better understanding of recent and long-term effects of cannabis is critical for informing public health policies. Meta-analytic evidence indicates that short-term effects of cannabis include decreases in cognitive performance (e.g., episodic verbal memory), but these reductions may not persist after 72 hours of abstinence,” Joshua L. Gowin, PhD, with the Department of Radiology at University of Colorado Anschutz Medical Campus, and colleagues explain. “Given the cognitive effects of cannabis and the disruption of the endogenous cannabinoid system by tetrahydrocannabinol (THC), it may be that brain regions with high cannabinoid 1 (CB1) receptor density might be altered by cannabis.”
Utilizing functional MR imaging, the team compared connectivity in the brains of over 1,000 individuals as they completed a series of tasks related to memory, reward processing, emotion, language perception, motor skills, relational assessment, and theory of mind. The cohort was divided into three groups based on history of cannabis use—heavy, moderate and never. Heavy cannabis consumers were defined based on lifetime of 1,000 or more incidents of marijuana intake, while moderate study subjects reported 10 to 999 lifetime uses. Urine toxicology helped determine recent ingestion of the drug.
Compared to the moderate and nonusers, heavy users displayed lower activation in the anterior insula, medial prefrontal cortex, and dorsolateral prefrontal cortex during working memory tasks. Recent use was associated with lower activation during both memory and motor tasks, though these associations did not survive false discovery rate correction.
“These are regions that have a relatively high density of CB1 receptors and where receptor availability was found to be reduced in association with daily cannabis exposure,” the authors explain. “Similarly, rodent studies showed that THC exposure reduced the density and sensitivity of CB1 receptors in these brain regions, providing evidence that heavy cannabis use can cause neural adaption.”
Their findings signal the negative effects of heavy cannabis use on neural function “may be long lasting,” even in the absence of recent use.
“Our findings highlight the need to educate cannabis users about the consequences of recent and heavy lifetime cannabis use on cognitively demanding working memory tasks,” they suggest. “Similarly, the association between heavy use and decreased brain function could motivate regular cannabis users to reduce their cannabis use and could encourage treatment.”
Learn more about the findings here.
In addition to her background in journalism, Hannah also has patient-facing experience in clinical settings, having spent more than 12 years working as a registered rad tech. She began covering the medical imaging industry for Innovate Healthcare in 2021.