Largest Study to Date Finds Decreased Brain Function in Younger Cannabis Users

The most extensive study to date on cannabis effects in 18- to 36-year-olds reveals that the drug can impair brain function during cognitive tests. These findings aim to help individuals make informed choices about cannabis use.

With the growing legalization of cannabis for both medical and recreational use, debate continues over its safety, particularly for young adults. Since brain development extends through the mid-to-late 20s, adolescence remains a crucial period for cognitive growth.

Previous studies on cannabis use and brain function in young adults have been limited in scale, but a new study led by researchers at the University of Colorado is the largest to date.

“As cannabis use continues to rise worldwide, understanding its effects on human health has become increasingly important,” said Joshua Gowin, PhD, assistant professor of radiology at the University of Colorado School of Medicine on the Anschutz Medical Campus. “By examining both the benefits and risks, we can help individuals make informed choices and fully grasp the potential consequences.”

Participant Demographics and Data Collection

The study analyzed data from 1,003 adults aged 22 to 36, including MRI scans, urine toxicology results, and self-reported cannabis use. The participants had an average age of 28.7 years, with 53.1% identifying as female. The sample was predominantly White (76%), but also included Black (13.7%) and Asian (6.3%) participants.

To determine recent cannabis use, participants provided a urine sample on the same day as their MRI scan, which was tested for a THC metabolite. A positive result categorized them as recent users. Lifetime cannabis use was also assessed: heavy users had consumed cannabis 1,000 or more times, moderate users between 11 and 1,000 times, and non-users fewer than 10 times. MRI scans measured brain activity while participants completed seven cognitive tasks evaluating emotion, reward processing, motor function, working memory, language, logical reasoning, and social cognition.

The findings revealed that both recent cannabis use and heavy lifetime use were linked to a statistically significant decline in brain activity—but only during the working memory task.

Participant Demographics and Data Collection

“We applied rigorous research standards and statistical corrections to minimize false positives,” Gowin said. “While some tasks hinted at cognitive impairment, only the working memory task showed a significant effect.”

Working memory temporarily stores and retrieves information for decision-making and behavior, such as following directions or tracking a conversation.

Heavy cannabis users showed reduced brain activity in three key regions: the dorsolateral and dorsomedial prefrontal cortex and the anterior insula, all crucial for reasoning, emotion, and social behavior.

The researchers suggest that recent users may benefit from abstaining before cognitively demanding tasks. However, heavy users may face withdrawal symptoms, which could also affect performance.

“The ideal abstinence period is unclear, but cognitive effects may persist for two to four weeks, and withdrawal in heavy users can last a week or more,” they noted.

The study cannot confirm a causal link between cannabis and brain function and is limited to young adults. It also lacked data on THC potency, CBD content, and consumption methods.

“There’s still much to learn about cannabis’s impact on the brain,” Gowin said. “Long-term studies are needed to understand its lasting effects and differences across age groups.”

Read the original article on: New Atlas

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