THC, the main psychoactive compound found in cannabis, has received increasing attention in recent years for its therapeutic potential. While it can reduce inflammation and shield neurons from damage, it can also impair learning and memory. This tradeoff has limited its use as a treatment for neurological disorders such as Alzheimer’s disease.
A recent study offers a possible solution. Scientists at the University of Texas Health Science Center at San Antonio found that combining a low-dose of THC with a commonly used anti-inflammatory drug improved cognition and reduced Alzheimer’s-related brain changes in mice.
The research, published in Aging and Disease, combined THC with celecoxib, a selective COX-2 inhibitor commonly prescribed for pain and arthritis. This approach could help retain the medical benefits of THC while reducing its cognitive side effects. It may also allow for faster progress toward clinical trials.
A Problem for the Brain
Evidence that inflammation plays a central role in neurodegenerative disease has grown alongside interest in THC as a therapeutic treatment. THC can reduce inflammatory signals and protect neurons under stress, but it can also impair memory and learning at low doses.
More than a decade ago, lead author Chu Chen began investigating the reasons behind this effect. His earlier research identified Cyclooxygenase-2 (COX-2) as a key factor. COX-2 is an enzyme best known for driving inflammation and pain.
“When THC is given, it unexpectedly increases COX-2 in the brain,” Chen said. “That increase is closely associated with learning and memory impairment.”
Blocking COX-2 alone has not proven effective. Previous Alzheimer’s trials using high doses of COX-2 inhibitors not only failed to improve cognition but also increased cardiovascular risks. The main challenge has been to reduce harmful inflammation without interfering with normal brain activity.
A Combination Approach
The researchers used a different approach in this study. Instead of targeting COX-2 by itself, they combined a very low dose of THC with a low dose of celecoxib. This strategy aimed to offset THC’s pro-inflammatory effects while preserving its neuroprotective properties.
The research team tested this combination in two mouse models of Alzheimer’s disease. One model developed beta-amyloid plaques, while the other developed tau tangles. Both of these features are common hallmarks of Alzheimer’s in humans.
The researchers began dosing the mice before any memory symptoms appeared. Mice received daily oral doses for 30 days. The regimen combined 3 milligrams per kilogram of THC and 1 milligram per kilogram of celecoxib, which would be equivalent to about 18 milligrams of THC and 6 milligrams of celecoxib per day for a 165-pound adult.
Improved Cognition, Reduced Pathology
On their own, low doses of THC improved some aspects of cognitive performance but also increased brain inflammation. The combination of THC and celecoxib performed better across the board. Mice that received both drugs showed improved learning and memory, lower levels of beta-amyloid and tau, and reduced signs of brain inflammation.
“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.”
Single-cell RNA sequencing supported these behavioral results. After treatment, genes related to synaptic function, inflammation, and Alzheimer’s risk shifted toward patterns seen in healthy brain tissue.
A Fast Track to Clinical Testing
Both compounds used in the study are already approved by the FDA. A synthetic form of THC is prescribed for chemotherapy-related nausea and appetite loss, while celecoxib has been used for many years to treat pain and inflammation.
This regulatory status could shorten the path to clinical testing. “If you develop a new compound, it can take 10 to 20 years to reach patients,” Chen said. “In this case, both drugs are already approved. That gives us a real advantage.”
The next step will be to test whether the drug combination can slow disease progression or restore cognitive function after symptoms appear. Even small delays in symptom onset could have important benefits.
Delaying the onset of Alzheimer’s symptoms by even a few years would ease the burden on patients, families, and healthcare systems. This study also adds to the growing evidence that cannabis-derived compounds may be most effective when used alongside other targeted drugs, rather than as standalone treatments.
“This work has taken many years,” Chen said. “But now we’re at a point where basic neuroscience discoveries are pointing toward something that could realistically move into the clinic.”
Austin Burgess is a writer and researcher with a background in sales, marketing, and data analytics. He holds a Master of Business Administration, a Bachelor of Science in Business Administration, and a Data Analytics certification. His work combines analytical training with a focus on emerging science, aerospace, and astronomical research.