Posted on: July 8, 2019 at 8:40 am
Last updated: December 2, 2019 at 8:03 pm

If someone were to ask you what the effects of marijuana were on the brain, you might be tempted to rely on the stereotypes that first come to mind. Dopey-ness, low energy, calmness, goofiness (and a strange penchant for salty snacks).


But a recently published animal study suggests that a certain cannabinoid could have the effect of enhancing cognitive function in seniors (at least in senior mice).

THC a Benefit for the Aging Brain?

Andreas Zimmer of the University of Bonn, Germany led a team of researchers in studying the effects of low doses of delta-9 tetrahydrocannabinol (more commonly known as THC) on young, adult, and aged mice.


When given a low subdermal dose of of THC, young mice exhibited slight impairments of memory and learning, such as finding a safe platform in a water maze or recognizing familiar mice.

Adult and aged mice, however, had the opposite effect. Without THC, they consistently performed worse than the THC-free young mice on memory and learning tests. But when administered low doses of THC, they performed better than usual- just as well as the fast-learning young mice, in fact.

The THC “reversed the age-related decline in cognitive performance of mice aged 12 and 18 months,” Zimmer reports. (Nature)

In fact, when the researchers examined brain imaging of their mice subjects, they found that THC-treated aged mice showed new synaptic spines developing in their hippocampus.


“The idea is that as animals grow old, similar to in humans, the activity of the endogenous cannabinoid system goes down—and that coincides with signs of aging in the brain,” Zimmer said. “So we thought, ‘What if we stimulate the system by supplying [externally produced] cannabinoids?’ ” (Scientific American)

So, what does this mean for human seniors?

“Restoration of CB1 signaling in old individuals could be an effective strategy to treat age-related cognitive impairments,” the research team concludes. (Nature) In other words, altering the endocannabinoid system of seniors to better respond to THC might have positive results on age-related memory loss and cognitive impairments.

Still, researchers caution that much more information is needed before anything can be assumed about THC’s effects for humans. “I don’t want to encourage anyone to use cannabis in any form based on this study,” Zimmer warned. (Scientific American)

Related: ‘Doctors Should Educate Themselves.’ Elderly Face Stigma As More of Them Are Relying On Marijuana for Relief

More Researchers Reconsider Marijuana’s Cognitive Effects

Not long after Zimmer’s researched was published in 2017, another team of scientists published their own meta-study on marijuana’s cognitive effects; they suggested that the negative effects often associated with marijuana use among young adults might not be as profound as once thought.

“Although continued cannabis use may be associated with small reductions in cognitive functioning, results suggest that cognitive deficits are substantially diminished with abstinence,” lead researcher Dr. J. Cobb Scott summarized. (JAMA, 2018)

Scott’s extensive analysis of 69 cross-sectional studies of 2152 cannabis users and 6575 comparison participants suggested that the “haze” (cognitive dysfunction) caused by cannabis use among young people did not seem to persist beyond a few days.

Dr. Sheryl A. Ryan, chairperson for AAP’s Committee on Substance Use and Prevention noted, however, that Scott’s meta-study didn’t include any long-term research, making it difficult to draw any conclusions.

So, what’s a person to think?

The Canadian Centre on Substance Use and Addiction (CCSA) released a report this year to help Canadians better understand the effects of marijuana, which is newly legalized in the country.

“The available evidence suggests that, for most individuals, chronic cannabis use does not produce severe or grossly debilitating impairment of cognitive functioning.

Instead, the effects appear to be more subtle and no longer measurable
after a few days to weeks of abstinence (Scott et al., 2018). However, initiating regular cannabis use in early adolescence and continuing through young adulthood can lead to more pronounced and long-term cognitive deficits (Meier et al., 2012; Morin et al., 2018).

There is ongoing debate about whether heavy cannabis use (e.g., daily
use) results in permanent changes in cognition or whether cognitive deficits are reversible after extended abstinence from the substance (Jackson et al., 2016; Meier et al., 2012; 2018; Morin et al., 2018; Volkow, Baler, Compton, & Weiss, 2014)”

Quote from the 2019 CCSA Report

You can view the CCSA’s complete report on cannabis’ cognitive effects for free here. It’s also recommended to review the NIH’s online summary of cannabis health and safety, found here.

Disclaimer: This information is not intended to be a substitute for professional medical advice, diagnosis or treatment and is for information only. Always seek the advice of your physician or another qualified health provider with any questions about your medical condition and/or current medication. Do not disregard professional medical advice or delay seeking advice or treatment because of something you have read here.

Read Next: Crohn’s Disease Treatment Could Be Another Of Benefit of Marijuana

Maria Sykes
Team Writer
Marie Sykes is an Ontario based writer with a background in research and a love for holistic wellness. She's especially interested in boosting awareness for women's health issues. Once a shunner of gyms, Marie has found an appreciation for weight training and HIIT circuits. She enjoys trying cuisine from all over the world, and she also enjoys not caring two cents what other people think her body should look like.

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