Forget short-term memory loss, people who have consumed cannabis at any point during their younger lives display larger volumes in brain regions linked to executive function, learning, and memory by the time they reach middle age, new research shows. However, these discoveries come with several caveats, as there are factors that complicate the long-term health effects of cannabis use.
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According to a study in PubMed, cannabis may influence brain health differently across people’s lifespans, potentially being more protective in older individuals while posing risks in earlier stage development. This study sought to assess the correlation between cannabis use and brain health in people ages 40 to 70.
Using data from the UK Biobank, which includes health data from over half a million adults, researchers analyzed associations between cannabis use, regional brain volume, and cognition in middle-aged and older adults (average age 54.5). Doctorate-credentialed researchers Anika Guha, Zening Fu, Vince Calhoun, and Kent E. Hutchison found that moderate lifetime cannabis use is associated with increased brain volume in the hippocampus, amygdala, caudate, and putamen, regions linked to emotion, motor control, and memory.
Examining data from 16,728 individuals, the researchers realized that moderate cannabis use was linked to better performance in tasks that engage learning, processing speed, and short-term memory, which is ironic considering that anecdotally, cannabis consumption is often stereotypically linked to short-term memory loss.
“I was a little surprised that every cognitive measure that demonstrated a significant effect showed better performance among cannabis users,” study co-author, clinical psychologist and faculty research associate in the Department of Psychiatry at CU Anschutz, Anika Guha, said in a statement. “It goes against your default assumptions, because I think a lot of research out there has shown cannabis is associated with worse cognitive function, at least acutely.”
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The researchers therefore suggest that while consuming cannabis may pose risks to adolescents (As famous cannabis user Whoopi Goldberg asserts, “No one is trying to get kids high.”), they do not appear to persist later in life. Instead, cannabis may protect the brain against age-related neurodegeneration and atrophy.
It’s currently unclear how the plant exerts these positive effects, although it’s noteworthy that all of the brain regions examined in this study contain high concentrations of CB1 receptors, which represent the primary binding site for cannabinoids (such as THC).
Therefore, the study’s authors speculate that activation of this receptor may help prevent brain shrinkage by balancing inflammation, immune function, and neurodegeneration, which is consistent with the endocannabinoid system’s role in restoring homeostasis.
Additionally, many of these regions are particularly prone to atrophy later in life, with hippocampal volume loss considered to be a significant cause of dementia. Therefore, the researchers are curious if cannabis might help to prevent certain types of cognitive decline.
“More older adults are using cannabis. It’s more widely available and is being used for different reasons than in younger folks – such as for sleep and chronic pain,” said Guha. “Plus, people are living longer. We have to be asking, ‘What are the long-term effects of cannabis use as we continue to age?’”
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Overall, the link between cannabis use, enhanced brain volume, and improved cognition was strongest in people who had consumed it moderately during their lives. Surprisingly, positive effects were recorded in people who hadn’t consumed cannabis for several decades prior to being evaluated.
Despite these findings, the study authors note that many factors remain unknown. For instance, cannabinoid use appears to affect the dichotomy of male and female brains, and the reasons for this are not described.
Perhaps it relates to the female amygdala reaching its maximal volume by age four and showing only a small increase in gray matter volume during adolescence. In contrast, the male amygdala increased by 53 percent between ages four and 18, according to another study in the National Library of Medicine. This contrast supports the adage that “girls mature faster than boys.”
Data on which cultivars, potency levels, and preferred consumption methods by sex are omitted. Nor do the researchers disclose how various cannabinoids –including cannabidiol (CBD), cannabinol (CBN), or cannabigerol (CBG)– might be directly involved.
“There’s so much more to explore,” said Guha. “We’re really interested in thinking about both the benefits and risks and understanding this in the context of mental health, dementia, and more.”
Overall, the conclusion is ambiguous, and the study authors conclude that “cannabis may influence brain health differently across the lifespan, potentially offering protective effects in older age while posing risks earlier in development.”