Recent research reveals a connection between extensive cannabis use over a person’s lifetime and reduced brain activity in areas responsible for working memory. © 24K-Production/Getty Images This article was first published on Healthline A new study indicates that frequent cannabis use can lead to a slight to moderate decline in working memory. Working memory is crucial for daily activities like driving, recalling a grocery list, and following verbal instructions. While the study is observational and cannot definitively prove that cannabis causes brain damage, it contributes to the growing body of evidence suggesting that cannabis may impact cognitive function. The study suggests that increased cannabis consumption could impair working memory, potentially causing difficulties in everyday tasks. “Working memory involves the ability to retain a small amount of information in the mind while carrying out a task,” explained Dr. Natalie Klag, an assistant professor of psychiatry at The Ohio State University Wexner Medical Center in Columbus. “It’s not just about remembering the information but being able to utilize it.” “This can encompass tasks such as adhering to instructions, making plans, or engaging with others in socially appropriate ways,” added Dr. Klag, who was not involved in the study. “Individuals with impaired working memory may struggle with following directions or completing multi-step tasks,” she told Healthline. “They may also encounter challenges in remembering questions or details in conversations long enough to respond when it’s their turn to speak,” she continued. “Moreover, they may face difficulties in complex reasoning that necessitates considering multiple pieces of information to make a decision.” Extensive cannabis use hampers cognitive function The observational study, released on January 28 in JAMA Network Open, does not conclusively establish that cannabis causes brain impairment; therefore, the results should be interpreted cautiously. Nevertheless, the study contributes to the growing body of evidence indicating that prolonged cannabis use may impact cognitive abilities, including memory. “I appreciate that the researchers examined seven different types of brain tests, but only one showed a mild association,” noted Dr. Sherry Yafai, an emergency medicine physician and director of integrated medicine at Providence Saint John’s Health & Wellness Institute in Santa Monica, CA. “I would prefer if the researchers boldly stated, ‘If you’re young, perhaps heavy cannabis use all day isn’t advisable. Being a heavy cannabis user is not recommended,’” added Dr. Yafai, who was not involved in the study. In the study, researchers analyzed data from the Human Connectome Project, investigating how age, development, diseases, and other factors influence the connections in the human brain. Between 2012 and 2015, more than 1,000 former or current cannabis users underwent functional MRI brain scans while performing seven cognitive tests. These tests included assessing working memory, which involves the brain’s processing of rewards, emotions, language, and motor skills. Working memory is also crucial in social contexts for processing significant social cues such as
Participants provided urine samples on the testing day to determine recent cannabis use. THC, the main psychoactive compound in weed, can be detected in urine for 3 days after single use and over 30 days after heavy use. Heavy cannabis use was linked to reduced brain activity in memory areas, independent of recent use or alcohol intake. Structural brain changes from heavy cannabis use may impact daily functioning, especially in young adults. Abstaining from cannabis before demanding tasks may improve performance, as cognitive effects may last 2-4 weeks. Cannabis dependence diagnosis was not linked to brain function changes, indicating negative cognitive effects can occur outside of formal dependence. Healthcare professionals should discuss harm reduction strategies to minimize cannabis use’s potential long-term consequences. Medical benefits of cannabis use were not explored in the study.
The study focused on young adults found notable disparities between individuals using cannabis throughout the day and those aged 75 and in the postmenopausal stage, specifically when using THC for sleep issues. Yafai, speaking to Healthline, highlighted that heavy cannabis users in the research tended to be male, with lower income and education levels, and increased alcohol consumption. These demographics make generalizing the results to other population groups challenging.
Moreover, the study was conducted between 2012 and 2015 when cannabis availability was more limited compared to the present, potentially biasing participants towards more determined seekers of cannabis. Yafai also raised concerns about the study’s failure to consider the impact of memory-affecting medications like benzodiazepines and antihistamines among the participants.
Yafai emphasized the importance of understanding the potential cognitive impacts of medications, stating that intoxicating substances can impair memory, including THC. Cautioning against driving under the influence, she also underlined potential performance issues at work or school due to intoxication.
Of particular concern for Yafai were individuals using cannabis for medical reasons, such as chronic pain or sleep aid, who might be alarmed by the study’s presentation of results. She urged individuals to have a conversation with their healthcare provider to weigh the benefits and risks of prescription medications and THC before making any decisions.
The study analyzed data from over 1,000 current or former cannabis users, aged 22 to 36 years, who underwent brain scans while performing cognitive tests. Heavy lifetime cannabis use, exceeding 1,000 times, was linked to reduced brain activity in regions associated with working memory, though the effect size was deemed small to medium.
While the study was observational and cannot definitively prove cannabis-related brain damage, it contributes to the growing body of evidence suggesting that frequent cannabis use may impact cognitive functions.
