“Pothead” could one day get a whole new meaning.
A new study suggests low doses of THC, the main psychoactive ingredient in cannabis, may protect memory and reduce brain damage linked to Alzheimer’s when combined with an anti-inflammatory medication.
The research was done in mice, but scientists say the fact that both drugs are already widely used could help speed the combo into human trials.
“If you develop a new compound, it can take 10 to 20 years to reach patients,” Dr. Chu Chen, a professor in the Department of Cellular and Integrative Physiology at UT Health San Antonio, said in a press release.
“In this case, both drugs are already approved,” he explained. “That gives us a real advantage.”
That’s potentially huge — especially since more than 7 million Americans currently have Alzheimer’s, and that number is expected to nearly double by 2060 unless scientists find new ways to prevent or cure it.
High hopes
In recent years, research into THC has found that it can have medical benefits, including anti-inflammatory and neuroprotective properties.
In the US, the FDA has already approved synthetic forms of the drug to treat chemotherapy-related nausea and appetite loss in cancer and HIV patients.
However, it has a downside: Studies have found THC can harm learning and memory, but the exact reason why wasn’t clear. So Chen set out to investigate.
Back in 2013, he identified a key culprit: COX-2, an enzyme linked to inflammation and pain.
Normally, COX-2 is low in a healthy brain — but it ramps up during injury, infection or disease.
It plays a unique role in learning and memory, helping the brain strengthen or weaken connections between neurons. But when COX-2 becomes overactive, it can also drive cognitive decline.
“When THC is given, it unexpectedly increases COX-2 in the brain,” Chen found in the study. “That increase is closely associated with learning and memory impairment.”
In the past, researchers tried giving Alzheimer’s patients COX-2 inhibitors, a class of medications that block the enzyme to reduce inflammation. But the treatment failed to improve their cognition, and it was linked to dangerous cardiovascular side effects.
That’s where Chen’s latest work takes a different route.
Tiny doses, big results
Endocannabinoids, cannabinoids produced naturally in the brain, act on the same receptors as THC but often have the opposite effect. One key endocannabinoid, 2-AG, reduces COX-2 activity and cuts neuroinflammation.
So Chen asked a simple question: Can we block THC’s inflammatory effects while keeping its benefits?
The answer may be yes — with a little help from celecoxib, an anti-inflammatory drug and COX-2 inhibitor widely prescribed for arthritis and pain.
In the study, researchers used very low doses of a THC extract and celecoxib, far below levels linked to heart risks in past Alzheimer’s trials.
Mice were given 3 mg per kg of THC and 1 mg per kg of celecoxib per day, the equivalent of about 18 mg THC and 6 mg celecoxib daily for a 165-pound person.
They tested the combination in two Alzheimer’s mouse models, one for beta-amyloid plaques and another for tau tangles, two hallmarks of the disease in the brain.
Treatment started before memory symptoms appeared in the mice so researchers could gauge whether the combo could prevent or delay Alzheimer’s. The mice were dosed once daily for 30 days.
The team found that low-dose THC alone improved some cognitive performance and reduced a few disease markers, but it also increased signs of inflammation.
The combination, however, produced stronger results, with improved learning and memory, reduced beta-amyloid plaques and tau tangles, and lower markers of brain inflammation.
Further analysis showed genes tied to brain function, inflammation and Alzheimer’s risk had also shifted back toward healthier levels after treatment.
“What really mattered was behavior,” Chen said. “If cognition is not improved, then the treatment doesn’t matter. And that’s where the combination clearly worked better than THC alone.”
What comes next
Looking ahead, the researchers are planning future studies to see whether the drug combo can slow disease progression or even reverse damage after symptoms appear.
“This work has taken many years. But now we’re at a point where basic neuroscience discoveries are pointing toward something that could realistically move into the clinic,” Chen said.
Experts say even delaying Alzheimer’s by just a few years would have a significant impact on patients, families and the healthcare system at large.
After all, the disease isn’t just memory loss. Over time, it slowly eats away at a person’s personality, thinking and reasoning skills, eventually making it difficult for them to perform even the simplest tasks.
On average, people live four to eight years after diagnosis. It was the sixth leading cause of death among Americans 65 and older in 2022, according to the Alzheimer’s Association.
And the risk is high: More than 1 in 9 people ages 65 and up has Alzheimer’s, and a 2025 study found that about 42% of Americans over 55 will develop dementia later in life, with Alzheimer’s being the most common form.
Across the country, surveys show that 92% of Americans would take a medication that could slow the disease — and nearly 3 in 5 would accept moderate or high risk to do so.
