Marijuana Impacts Memory
Source: Julia Milzer, "Largest Study Ever Done on Cannabis and Brain Function Finds Impact on Working Memory," University of Colorado, 28 January 2025.
"The researchers found that 63% of heavy lifetime cannabis users exhibited reduced brain activity during a working memory task, while 68% of recent users also demonstrated a similar impact."
"This decline in brain activity was associated with worse performance on working memory – the ability to retain and use information to perform tasks. For example, working memory allows a person to follow instructions they’ve just been given or to mentally visualize and manipulate information, like solving a math problem."
"During working memory tasks, the researchers found heavy cannabis use appeared to reduce brain activity in certain areas of the brain (dorsolateral prefrontal cortex, dorsomedial prefrontal cortex and anterior insula). These regions of the brain are involved in important cognitive functions such as decision-making, memory, attention and emotional processing."
Source: Joshua L. Gowin, "Brain Function Outcomes of Recent and Lifetime Cannabis Use," JAMA Network, 28 January 2025.
"In this cross-sectional study of 1003 young adults, heavy lifetime cannabis use was associated with lower brain activation during a working memory task; this association remained after removing individuals with recent cannabis use. These results were not explained by differences in demographic variables, age at first cannabis use, alcohol use, or nicotine use."
"These findings suggest that cannabis use is associated with short- and long-term brain function outcomes, especially during working memory tasks."
"Greater accessibility of cannabis has also been associated with higher rates of cannabis-related motor vehicle crashes, and frequent cannabis use is associated with increased risk for hyperemesis syndrome and cardiovascular disease. Despite these negative effects, there is an increasing perception that cannabis is harmless."
"The association we observed between recent use and working memory task activation and performance suggests that abstaining from cannabis prior to cognitively demanding situations will likely help with performance. The exact duration of this period of abstinence is unclear, but studies suggest that residual cognitive effects of cannabis may remain for 2 to 4 weeks after abstinence. Furthermore, in heavy users, abstaining from cannabis may also lead to withdrawal symptoms, which may last for a week or more following cessation and could also affect performance."
"Reduced brain activation to a theory of mind task was reported previously in cannabis users relative to healthy adults, and the study’s authors hypothesized that this could contribute to the increased risk of schizophrenia, a condition associated with profound deficits in theory of mind processes."
"In our study, we also observed reduced activation in recent cannabis users, which could contribute to the emergence of acute psychoses observed during THC intoxication, particularly for high THC doses."