Cannabis and Cognition: Do Long-Term Use Impacts Exist?

For years, cannabis has been at the center of debates regarding its impact on cognitive function, memory, and mental health – with some surprising studies to come out along the way.  With cannabis use on the rise, in the face of spreading legalization, such studies are crucial to expanding our understanding of the risk profile associated with cannabis.  With that in mind, a group of researchers recently provided fresh insights into the topic through a study¹ that looked at how lifetime and recent cannabis use affects brain activity, particularly in young adults.  Notably, in the study, cutting-edge neuroimaging techniques were used to explore these effects in an attempt to shed light on lingering concerns surrounding cannabis consumption.

The goal of this study was to better understand the impact that cannabis may have on neurological function over time.  To achieve this, the researchers made use of data from the Human Connectome Project.  This is a large-scale initiative that works to map neural connections in the brain.  From this data, the study focused on individuals between the ages of 22 to 36 that were further categorized by the following:

• Heavy Users: Individuals who reported more than 1,000 lifetime uses of cannabis.   
• Moderate Users: Those who had used cannabis between 10 and 999 times.
• Non-Users: Participants who had consumed cannabis fewer than 10 times in their lives.

From there, brain function across various tasks was assessed using fMRI scans.  These tasks included assessments of cognitive processes like working memory, reward processing, emotional regulation, motor skills, relational reasoning, language comprehension, and theory of mind (the ability to understand others’ perspectives).

One of the most notable discoveries from the data was an association between heavy cannabis use and reduced brain activation during working memory tasks.  More specifically, fMRI scans revealed decreased activation in key areas of the brain such as the anterior insula, medial prefrontal cortex, and dorsolateral prefrontal cortex.  This is notable, as these regions are believed to facilitate executive functioning, decision-making, and cognitive control.

These findings remained significant even after researchers adjusted for other factors such as age of first cannabis use, alcohol and nicotine consumption, and demographic differences.  Looking deeper, it was found that the patterns persisted even when excluding recent users.  This means that cannabis could potentially have a long-lasting impact on cognitive performance.   

Short-Term vs. Long-Term Effects

While lifetime cannabis use showed a strong correlation with brain activity changes, the researchers went a step further and also looked at the effects of recent use.  Upon doing so, it was found that the effects were not statically relevant – meaning that short-term use may not be as potentially harmful/pronounced as long-term use.

Implications of the Study

The results of the study highlight the importance of considering both lifetime and recent cannabis use when evaluating its impact on the brain.  Its findings suggest that heavy and prolonged cannabis consumption may lead to alterations in brain function, particularly in areas associated with memory and executive function.  However, a lack of strong correlations with other cognitive tasks clearly points to the fact that the effects of cannabis use on the brain are complex and not yet fully understood.

It is important to note that this study has limitations.  Being a cross-sectional study, no causality could be established – and we all know that correlation does not infer causation.  Furthermore, the study is only relevant to the age group included.  Finally, and quite importantly, the study did not have data on the exact timing of recent cannabis use or the potency of cannabis used, which could influence the results.

While more research is needed, this study reinforces the importance of moderation and informed decision-making when it comes to cannabis use.  With increasing legalization and acceptance of cannabis across society, our scientific understanding of cannabis’s effects on the brain must continue to grow.

By staying informed and considering emerging research, you can make a more conscious choice about your consumption habits, weighing the pros and cons of cannabis.

Study Reference:

^{1. Gowin, J. L., Ellingson, J. M., Karoly, H. C., et al. (2025). Brain function outcomes of recent and lifetime cannabis use. JAMA Network Open, 8(1), e2457069. https://doi.org/10.1001/jamanetworkopen.2024.57069}