The Leaf THE LEAF November-December 2019 | Page 17

Daily dose of cannabis extract could reverse brain's decline in old age, study
suggests – Neuroscience 8 th May 2018
Regular low doses of THC dramatically
boosted memory and learning in older mice,
say scientists, who plan a clinical trial in
humans later this year
Researchers have come up with an unusual
proposal to slow, or even reverse, the
cognitive decline that comes with old age:
small, daily doses of cannabis extract.
The idea emerged from tests on mice which
found that regular, low doses of
tetrahydrocannabinol (THC) – the main
psychoactive ingredient in cannabis –
impaired memory and learning in young
animals, but boosted the performance of old
ones.
The discovery has raised hopes for a treatment
that improves brain function in old age
without inducing the behavioural effects well
known to recreational users of the drug.
To investigate whether it works in humans,
the scientists plan to launch a clinical trial
later this year.
“If we can rejuvenate the brain so that
everybody gets five to 10 more years without
needing extra care then that is more than we
could have imagined,” said Andras Bilkei-
Gorzo at the University of Bonn.
Research on cannabis use by adolescents has
found compelling evidence that regular,
heavy use can impair the memory. But the
impact of the drug on older people’s brains
has been far less well studied.
Writing in the journal Nature Medicine, the
scientists describe how they gave a month-
long course of daily THC to mice aged two
months, one year, and 18 months.
The mice were then tested to see how fast they
solved a water maze, and how quickly they
recognised familiar objects such as mice they
had met before.
Without the drug, the younger mice aced the
tests, while the older ones struggled. But
infusions of THC had a dramatic impact on
both groups.
The performance of the younger mice
plummeted on THC, while older mice
improved so much that their scores matched
those of healthy drug-free young mice.
The benefits lasted for weeks after the
infusions ended. None of the mice displayed
the strange effects one might expect from
doses of THC.
“These results reveal a profound, long-lasting
improvement of cognitive performance
resulting from a low dose of THC treatment
in mature and old animals,” the scientists
write.
The boost in brain function was linked to an
apparent restoration of gene expression in the
brain to more youthful levels.
The German team believes that the drug
works by stimulating what is known as the
endocannabinoid system, a biochemical
pathway that becomes less active with age in
mice, humans and other animals. “I’m sure
that what we are seeing are the long-term
consequences of normalising the system,”
Bilkei-Gorzo said.