A groundbreaking new study published Tuesday in JAMA Network Open explores the effects of both recent and lifetime cannabis use on brain function, specifically during cognitive tasks that assess working memory. This study is the largest of its kind, involving over 1,000 young adults aged 22 to 36 and utilizing advanced brain imaging technology.
The researchers discovered that 63% of heavy lifetime cannabis users showed reduced brain activity during a working memory task, while 68% of recent users exhibited a similar decline. Working memory—the ability to retain and manipulate information—is crucial for tasks like following instructions or solving problems, such as doing mental math.
“This study underscores the growing need to understand the effects of cannabis use on cognitive health as its use becomes more widespread globally,” said Joshua Gowin, PhD, assistant professor of radiology at the University of Colorado School of Medicine and the study’s first author. “By studying these effects, we aim to provide a well-rounded understanding of both the benefits and risks of cannabis use, empowering individuals to make informed decisions about their health.”
The study classified cannabis users into three groups: heavy users (those who’ve consumed cannabis more than 1,000 times in their lifetime), moderate users (10 to 999 times), and non-users (fewer than 10 times). Participants underwent brain imaging (MRI) and completed seven cognitive tasks assessing working memory, reward, emotion, language, motor skills, relational assessment, and theory of mind.
The results revealed that cannabis use had a statistically significant effect on brain function during working memory tasks, meaning the findings were highly unlikely to be due to chance. The other cognitive tasks showed some potential effects, but these were not statistically significant.
“We took great care in ensuring the robustness of our findings,” Gowin noted. “By applying the highest standards and rigorous statistical corrections, we minimized the risk of false positives. The working memory task stood out as the only one showing a clear and statistically significant effect from cannabis use.”
The study found that heavy cannabis use appeared to reduce brain activity in specific regions associated with crucial cognitive functions, including the dorsolateral prefrontal cortex, dorsomedial prefrontal cortex, and anterior insula. These areas are involved in decision-making, memory, attention, and emotional processing.
Gowin also pointed out that the research suggests abstaining from cannabis before engaging in cognitive tasks could help improve performance. “People need to assess their relationship with cannabis carefully,” he said. “While sudden cessation could disrupt cognition, especially for heavy users, taking breaks from cannabis may benefit cognitive function.”
He added: “This study raises many important questions, and we need larger, long-term studies to understand whether cannabis use directly alters brain function, how long these effects persist, and how different age groups may be affected.”
As cannabis use continues to rise, research like this provides valuable insights into its potential cognitive effects and highlights the importance of ongoing studies to inform public health and decision-making.
