Cannabis could reverse brain decline

Cannabis has the potential to reverse brain ageing and improve memory function, a new European study has revealed.

Scientists at the University of Bonn and The Hebrew University of Jerusalem have achieved this in mice. They administered a low dose of THC, the active ingredient in the hemp plant (cannabis), to mice aged two, 12 and 18 months over a period of four weeks. Afterwards, they tested learning capacity and memory performance in the animals — including, for instance, orientation skills and the recognition of other mice. Mice who were only given a placebo displayed natural age-dependent learning and memory losses. In contrast, the cognitive functions of the animals treated with cannabis were just as good as the two-month-old control animals.

“The treatment completely reversed the loss of performance in the old animals,” reported Professor Andreas Zimmer from the Institute of Molecular Psychiatry at the University of Bonn and member of the Cluster of Excellence ImmunoSensation. This opens up new options, for instance, when it comes to treating dementia.

THC

First of all, the scientists discovered that the brain ages much faster when mice do not possess any functional receptors for THC. These cannabinoid 1 (CB1) receptors are proteins to which the substances dock and thus trigger a signal chain. CB1 is also the reason for the intoxicating effect of THC in cannabis products, such as hashish or marihuana, which accumulate at the receptor. THC imitates the effect of cannabinoids produced naturally in the body, which fulfil important functions in the brain. “With increasing age, the quantity of the cannabinoids naturally formed in the brain reduces,” said Zimmer. “When the activity of the cannabinoid system declines, we find rapid ageing in the brain.”

To discover precisely what effect the THC treatment has in old mice, the researchers examined the brain tissue and gene activity of the treated mice. The findings were surprising: the molecular signature no longer corresponded to that of old animals, but was instead very similar to that of young animals. The number of links between the nerve cells in the brain also increased again, which is an important prerequisite for learning ability. “It looked as though the THC treatment turned back the molecular clock,” said Zimmer.

Next step

A small quantity of the administered THC was chosen so that there was no intoxicating effect in the mice. Cannabis products are already permitted as medications, for instance as pain relief. As a next step, the researchers want to conduct a clinical trial to investigate whether THC also reverses ageing processes in the brain in humans and can increase cognitive ability.