Close-up of Marijuana plants

Health Update: Cannabis May Reverse Aging in Older Brains

In one of the stranger pieces of research news to hit the internet this week, cannabis appears to have the opposite effect on older brains than on younger brains. Mouse brains, that is.

THC, the main active ingredient in cannabis, befuddled younger mice in a study conducted by teams of researchers at the University of Bonn and the Hebrew University of Jerusalem, but in older mice it reversed cognitive declines, actually restoring brains on a biological level. The study was published in the May issue of Nature Medicine.

Pot has already been shown to reduce inflammation and help with chronic pain. Maybe it’s also the future of dementia treatment.

Not So Dazed & Confused

In their study, the researchers gave low doses of delta 9-tetrahydrocannabinol, or THC, to older, middle-aged and younger mice. (Parallel groups of mice received placebos.) Before being dosed up, older and middle-aged mice performed less well on tests of memory and learning than the younger mice did. Predictably, after being given THC, the performance of younger and mature mice declined—they flunked, just like dazed and confused teenagers. But the old mice’s performance improved. In fact, once they’d been given their doses of THC, the old mice did as well as the young ones did before their treatment.

And after four weeks of receiving a low dose of THC via a 24/7 drip feed, age-related losses in memory and learning had been completely reversed in the older and middle-aged mice. But the young mice that had been treated performed just as badly as the older, untreated mice.

On examining the brain tissue and genetic activity of the treated mature mice, the researchers discovered something unexpected: the brains of the old mice that had been treated with THC looked more like those of the 2-month-olds than the brains of the untreated older mice. And the changes had occurred at a molecular level—that means the changes were biological and not just behavioral.

According to an article in Scientific American, scientists unconnected to the study have praised its methods but caution that what seems to be true of mice may not bear out for humans. Still, there are good reasons why THC may improve cognition in older brains.

Why THC May Reverse Cognitive Aging

Mammalian brains naturally contain cannabinoid molecules in what’s known as a cannabinoid system that mediates things like appetite, pain-sensation, memory and other cognitive processes. As we age, our cannabinoid systems slow down—one factor that scientists believe may be responsible for cognitive decline.

“The young brain has lots of endocannabinoids, and an old brain has significantly less,” Onder Albayram, one of the study’s authors, told Inverse. “That’s why when you give THC to a young brain, which can access lots of endocannabinoids, this confuses the brain. But when you give THC to old brains, they have less endocannabinoid binding affinity, so the brain experiences a plasticity change to adapt to high THC.” In other words, in older mice, administering THC restored a balance.

According to Albayram, mouse brains and human brains, and their cannabinoid systems, are very similar. Next up: studies to evaluate the effects of THC in older humans—how much, how often and for how long.

A word of caution: The amounts of THC administered to the mice were relatively small. The researchers don’t know if too much—say, the amount you might be expose to through regular recreational use—might have the opposite effect and exacerbate rather than reverse losses in memory and the capacity to learn.

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