Ultra-low dose of delta-9 tetrahydrocannabinol (THC) has been shown to reverse cognitive impairments as a result of old age or Familial Alzheimer's Disease.
After receiving a single injection of this ultra-low dose of THC, old mice showed significant improvement over controls in measures of memory and learning and the beneficial effect of THC lasted for at least 7 weeks.
A similar effect occurred in a mice model for Familial Alzheimer's Disease (5xFAD). A single injection of ultra-low THC showed cognitive improvement when administered after the onset of Alzheimer's behavioral symptoms.