A recent study published in JAMA Network Open has raised concerns about the impact of frequent marijuana use on cognitive functions, particularly working memory, which is critical for tasks such as communication, decision-making, and job performance. Cannabis, one of the most widely used illicit substances globally, is consumed by approximately 147 million people each year. The research brings attention to the potential long-term consequences of frequent cannabis use, especially for those in demanding work environments.
The study analyzed data from more than 1,000 participants who were part of the Human Connectome Project conducted between 2012 and 2015. These participants, aged between 22 and 36, underwent brain scans while performing cognitive tests designed to measure their memory, decision-making, emotional processing, and social interactions. The researchers categorized participants based on their cannabis consumption: heavy users (those with over 1,000 lifetime uses), moderate users (10-999 uses), and non-users (fewer than 10 uses).
The results revealed that heavy cannabis users exhibited significantly reduced brain activity in regions associated with memory and decision-making. This reduced activity may have real-world implications, as working memory is essential for tasks such as driving, where individuals need to briefly store and use information to make safe decisions, or responding appropriately in a conversation, such as a work-related discussion with a supervisor. Dr. Joshua Gowin, the lead author of the study and assistant professor of radiology at the University of Colorado’s Anschutz School of Medicine, explained that working memory allows individuals to retain critical information momentarily, which is vital for many everyday tasks.
However, while the study highlights a strong connection between cannabis use and impaired memory, it does not establish a direct cause-and-effect relationship. Carol Boyd, a professor emerita at the University of Michigan, pointed out that while the stereotype of the forgetful cannabis user has existed for years, a major question remains: Can working memory improve after quitting cannabis use? Boyd suggests that further research is needed to understand whether individuals who cease heavy cannabis use can recover their cognitive abilities over time.
The study also found that heavy cannabis users demonstrated about 14 percent less brain activation compared to non-users, particularly during memory-related tasks. Additionally, recent cannabis use appeared to have a more immediate effect on brain activity than long-term use. Despite these findings, the study did not explore whether memory recovery is possible after prolonged abstinence from cannabis.
Other factors, such as Attention Deficit Hyperactivity Disorder (ADHD), which is also linked to memory issues, were not fully considered in the study. Moreover, the research did not measure tetrahydrocannabinol (THC) levels in the participants or differentiate between various methods of cannabis consumption, such as smoking versus edibles, which could influence the effects on memory.
The long-term effects of cannabis on cognitive function remain an area of active research. Some studies suggest that abstaining from cannabis for even a month may lead to partial recovery of memory, but conclusive evidence is still lacking.
In Kenya, the use of cannabis is on the rise, with nearly one million individuals, including a significant number of young people aged 15-24, reported to be regular users. According to the National Authority for the Campaign Against Alcohol and Drug Abuse (NACADA), there has been a dramatic 90 percent increase in cannabis consumption in the past five years. This upward trend has raised significant public health concerns, as heavy cannabis use is not only linked to impaired cognitive function but also to increased risks of mental health disorders, lung damage, and adverse effects during pregnancy.
The World Health Organization (WHO) has also warned that cannabis use, especially during adolescence or early adulthood, can hinder learning and memory. Chronic use can result in lasting cognitive damage, which may not fully reverse even after cessation. As cannabis use continues to grow globally, understanding its long-term effects on the brain is crucial for public health initiatives aimed at mitigating its negative impact.
In conclusion, while the study provides compelling evidence of the cognitive risks associated with frequent cannabis use, it also underscores the need for more research to fully understand the long-term consequences and the potential for recovery after quitting.
