THC (found in cannabis) that was given to old mice improved performance on learning and memory tests, improved connections between neurons, and resulted in gene activation profiles in the hippocampus that resembled young mice.
The mice that were 12 months old (mature mice) and 18 months old (old mice) both performed better after given THC and this on was dependant on activation of glutamatergic CB1 receptors and histone acetylation that was induced by THC.
In contrast, young mice given THC performed worse on memory tests. The mice termed “young” in this study were 2 months old. They performed worse on memory tests after given THC. Typically a mouse is termed “adult” if it is 3 months old. It seems possible that some brain development may still occur at 2 months of age but I’m not sure.
It is unclear whether THC will improve memory in older adults but this preclinical study provides strong evidence along with a mechanism that it might.