Use of marijuana appears to boost the function of brain circuits and delay the onset of cognitive decline in mice, researchers reported.
When tested in a rodent model that replicates human behavior affected by age-related cognitive impairment, drugs such as up to 10 milligrams per kilogram/day (mg/kg) of THC, the component of marijuana that makes people high, appeared to provide a mild cognitive benefit comparable to using a placebo, according to the researchers.
The effect of THC was similar to the effect of placebo, said the researchers. THC and placebo were given at doses of 50 mg and 100 mg, respectively, daily.
Subsequent administration with THC at that dosage resulted in modest delay in cognitive impairment even when THC was reintroduced several weeks later, the researchers showed3.
“The results are encouraging because we observed a deficit in function impairment even at higher doses administered as THC-agonists, particularly in middle-age mice, ” said study lead author Ethan J. Roberts, a UC Davis Professor of Psychology.
Roberts, the world’s first professor of cognitive neuroscience, said the study could lead to a critical shift in interest in the development of new therapies for age-related cognitive impairment.
“We still have no good drugs to treat cognitive decline, but we do know that THC works by modulating the activation of certain brain circuits in the brain, ” Roberts said.
Roberts pointed to how THC stops brain cells in their tracks as well as to chemically change their nuclei, which could signal how effective THC is.
Pot and its cousin THC, or tetrahydrocannabinol, can make a person high, or “high. ” The two are chemically different compounds. Many drugs used to treat alcohol abuse also act similarly to THC.
Roberts said THC was introduced by smoking the plant to test its effects on cognition. He said it was not given to mice first, but took over half of their rations of THC in order to achieve the effects.
McGinty added that the model of human cognition that Roberts was testing is very different from that of mice and humans, meaning it will not necessarily apply to people living with cognitive deterioration.
The study was conducted in the same rat despite the fact that Roberts said it is unlikely a mouse model will respond to a human experiment regarding cognition. The researchers say that the data for the study is not representative.
“Our effective control is far more small in that we do not measure any cognitive impairment prior to when THC exposure lasts to help us understand how long-term THC treatment might be needed in healthy humans, ” McGinty said.
The idea to test THC drug and placebo in healthy humans began because Roberts thought such tests would be valuable in monitoring the effect of cannabinoids.
Roberts continued to worry that THC could potentially cause cognitive impairment in aging.
“The most reassuring finding from our analysis was that THC appears to make the brain circuits more resilient, ” he said. “Recent clinical data of minimize cognitive impairment has shown that THC appears to be generally safe and well tolerated, demonstrating an absence of more serious side effects, ” he said.
Roberts said the THC gene-edited rodents show some evidence of cognitive impairment. “In fact, THC appears to have inactivated the cognitive networks affected by age so that there’s less loss of cognitive function, ” he said. “Seeing how THC alters specific regions within the visual system was not unexpected. “