Employers, monitor Marijuana use by employees in the workplace. TestSource Lab can help

Largest Study of Its Kind Finds How Long-Term Cannabis Use Affects Memory The findings appeared in the journal JAMA Network Open.

In the United States alone, nearly half of all states have legalized recreational cannabis, and its use is on the rise. Yet, despite its growing acceptance, the long-term effects of cannabis on the brain remain poorly understood.

In a world where cannabis is increasingly legalized and normalized, questions about its effects on the brain have never been more pressing. A recent study, the largest and most comprehensive of its kind, offers some of the clearest insights yet into how cannabis use affects brain function during cognitive tasks.

The study’s findings align with earlier research showing that cannabis use can alter brain structure and function. For example, studies have found that heavy cannabis use is associated with reduced thickness in the prefrontal cortex, a region involved in decision-making and self-control. However, these weren’t causal links. One could argue that people with these innate cognitive characteristics are more prone to cannabis use in the first place.

Other research has shown that cannabis can disrupt the brain’s endocannabinoid system, which plays a key role in regulating mood, memory, and appetite.

But the new study goes further by examining how these changes manifest during specific cognitive tasks. The reduced brain activation seen in heavy users could help explain why some people who use cannabis heavily struggle with memory and attention in their daily lives. It also raises concerns about the potential long-term consequences of cannabis use, especially for young people whose brains are still developing.

Using advanced brain imaging technology, the researchers discovered that 63% of heavy lifetime cannabis users and 68% of recent users exhibited diminished brain activity during working memory tasks. This decline was associated with poorer performance on tasks that require holding and manipulating information, such as following instructions or solving a simple math problem.