Marijuana use has been charged with hurting our memory, especially after long years of heavy use starting at a young age. But now, a joint study conducted by German and Israeli scientists has found that the active ingredient in pot improves memory performance and cognitive functioning in old mice when given in small controlled doses. The discovery could pave the way for new treatments for human dementia, the scientists suggest.
While the doses were too small to make the mice high, it did improve their learning and memory performance markedly, according to the scientists. Regarding their mental state, the marijuana turned the mice into frisky two-month olds, which in mouse years means young adulthood.
“The treatment completely reversed the loss of performance in the old animals,” stated Prof. Andreas Zimmer from the Institute of Molecular Psychiatry at the University of Bonn.
Why go there
You might be wondering, "Why on earth would the scientists even think to check whether pot improves memory in doddering rodents?"
Because they realized, both at the University of Bonn and, in different contexts, at the Hebrew University of Jerusalem, that the active ingredient in marijuana, if administered judiciously, had a good effect on elderly people – and not just by making them forget their troubles.
"Professor Itai Bab (since deceased) set out in 2009 to understand how cannabis affects osteoporosis in the aged," says Dr. Mona Dvir-Ginzberg, an expert on epigenetics at the Hebrew University of Jerusalem, who collaborated in the study. Her job was to analyze the effect that tetrahydrocannabinol (THC) has on our chromosomes.
Reports of marijuana impairing our cognitive functioning are based on self-reported use by people who aren't sticking to tiny controlled doses that don't knock them off their feet, explains Dvir-Ginzberg. They're flooding their systems with intoxicants. In other words, the effects are not comparable.
Losing our minds – and receptors
How does marijuana affect us when we partake, whether by brownie, or in a lab? We have receptors in our brain cells to which THC, the active ingredient in cannabis, docks. When the THC molecule docks in our receptor, a biochemical chain is set off.
In nature, the THC receptors evolved for biochemicals – endocannabinoids – that our bodies make, says Dvir-Ginzberg. Put otherwise, THC from pot we smoke or consume in any other way imitates the effect of cannabinoids we make naturally in the body.
It turns out that as we age, we not only lose our minds, but our THC receptors, too. Or in any case, their density lessens, a correlation that bore investigation.
The next discovery behind the present research was that in mice, the brain ages much faster when the rodents have no functional receptors for THC. From all this, the road to administering small, non-intoxicating doses of THC to elderly mice was short.
Dvir-Ginzberg points out that the teams didn't set out to study the effect of small controlled doses of THC on young mice, but on old ones with significant deterioration of brain function compared with the young mice.
The tested mice were aged two months, twelve months and 18 months, which made them pretty old, considering that mice have a short life span. Mice given a placebo (i.e., not THC) displayed natural age-dependent learning and memory losses, say the teams, while the mice treated with hemp did as well as the two-month-old control whippersnappers.
Brain performance in mice is tested by learning capacity and memory performance – recognizing other mice, for example.
"My role was to check for changes at the genomic level in the memory center of the brain," says Dvir-Ginzberg. Upshot: old mice given THC experienced epigenetic changes to their DNA that made them like young mice.
Moreover, the number of links between the nerve cells in the brain also rose anew, which is an important prerequisite for learning ability. “It looked as though the THC treatment turned back the molecular clock,” commented Prof. Andreas Zimmer of the Institute of Molecular Psychiatry at the University of Bonn.
So, should you spike Granny's tea? No. The next step, say the researchers, is to pursue clinical trials on elderly people to see if their brains also benefit from wee doses of THC. Putting pot in her drink probably would have an effect on grandma, but not that one. And if you get the dose wrong, which you will, she might find you funny, but won't remember the experience any better.
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