The world is hungry to understand how cannabis works. Both medical and recreational effects are coveted across many cultures and traverse ages. There are weed lovers everywhere, but until the last few years, there was minimal research on the plant.
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Now that more countries and states have legalized cannabis, short-term and long-term research is more rapidly available. A recently published study shared that regular, lifetime use may negatively impact brain function. This seems all bad, but there is a silver lining to the heavily reported story.
Every study has its limitations
Before getting to the heart of the data, there are study limitations to note. The research only mined young people, didn’t clock when people had last consumed before testing, and had no indication of what kind of weed products people used. This substantially reduced the scope of relevant data.
There was also a tiny representation of heavy and moderate users. A larger sample size is required for a true understanding of long-term effects. Lastly, there was no examination of psychiatric comorbidities, which could potentially impact outcomes.
The study was funded by a National Institute of Mental Health grant. The doctors who authored it also received grants from the National Institutes of Health and various foundations. One researcher was also supported by educational institutions.
These limitations are worth noting, but another nugget of wisdom has evaded the headlines.
The study in question: cannabis and brain function
Over 1000 young adults with a lifetime of heavy cannabis use took part in this cross-sectional study, which looked at how short-and-long-term consumption impacts the brain. Study authors used a range of tests to understand any potential connection between a lifetime history of being stoned and how the brain functions.
Data came from the Human Connectome Project and covered people aged 22 to 36 from August 2012 to 2015. This included MRI results, urine toxicology reports, and cannabis history.
Those with 1000 cannabis sessions under their belts were categorized as heavy lifetime cannabis users. Those who had enjoyed weed 10 to 9999 times were considered moderate users. Anyone who had fewer than 10 memories of marijuana was referred to as nonusers. Researchers verified self-reported use against urine analysis and included a diagnosis of cannabis dependence when necessary.
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In total, 53 percent of participants were women, and 47 percent were men. 76 percent of the sample group was white, 13 percent were Black, and 6 percent were Asian. Only about nine percent were classified as heavy cannabis users, 18 percent were moderate, and the majority (73 percent) were nonusers.
What they learned
Researchers set up tests and read data to understand how these people’s memory, emotion, reward response, language, motor function, perception of relationships, and ability to understand differing opinions may be impacted (theory of mind).
The big research paper’s big conclusion was that long-term use showed a lower brain activation related to working memory. This effect was quantified as having a “small to medium impact” by the study authors.
“Brain activation levels during the working memory task were associated with verbal episodic memory performance, intelligence, and education, suggesting that they are meaningful indicators of cognitive function,” the study reads.
This potentially negative news has gotten all the glory, but there is a silver lining. These researchers looked into more than memory. Brain imaging tasks covered the neural responses related to emotion, reward, motor function, language, relational reasoning, logic, social information processing, and theory of mind. None of these were associated with cannabis consumption or a dependence diagnosis.
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Researchers identified an association between recent use and poor performance for working memory and motor tasks. However, the association did not survive a statistical method that weeds out false discoveries. The headline has widely been that cannabis damages working memory, but the study also failed to show any negative impact on eight other neural responses.
Cannabis brain research paper not the end-all
With limitations in mind, researchers noted that the findings only indicate a need for deeper inquiry. This is the only way to show that cannabis consumption alters brain function and to understand how long that potential impact may last.
After a long dry spell, cannabis research seems more readily available than ever before. While pouring over new data can be fun, keep in mind that understanding the scientific assessment of this plant only comes with taking a wide scope to the topic. One weed study does not dictate truth, but it does add to the growing mosaic of understanding.
