Prolonged low-dose treatment with a marijuana compound may help reverse memory loss and improve cognitive skills, a finding that could pave the way for slowing brain ageing or treating dementia in humans, researchers say.

According to the study, the brain ages much faster when mice do not possess any functional receptors for tetrahydrocannabinol, or THC -- the chemical responsible for most of marijuana's psychological effects.However, treatment with 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. When the activity of the cannabinoid system declines, we find rapid ageing in the brain," said Andreas Zimmer, professor at the University of Bonn in Germany.

In the study, the researchers administered a small quantity of THC to mice aged two, 12 and 18 months over a period of four weeks.The results revealed that the cognitive functions of the older mice were just as good as the two-month-old mice."The treatment completely reversed the loss of performance in the old animals. It looked as though the THC treatment turned back the molecular clock," Zimmer said.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.