A chemical found in cannabis, known as tetrahydrocannabinol, or THC, has been found to potentially slow the process in which mental decline can occur in up to 50 percent of HIV patients, according to a new study carried by Michigan State University.

“It’s believed that cognitive function decreases in many of those with HIV partly due to chronic inflammation that occurs in the brain,” said Norbert Kaminski, lead author of the study, now published in the journal AIDS. “This happens because the immune system is constantly being stimulated to fight off disease.”

The researchers took blood samples from 40 HIV patients who reported whether or not they used cannabis; then, they isolated the white blood cells from each donor and studied inflammatory cells levels and the effect cannabis had on each cell.

The study found the compounds in cannabis were able to act as anti-inflammatory agents, reducing the number of inflammatory white blood cells, called monocytes, and decreasing the proteins they release in the body.

“This decrease of cells could slow down, or maybe even stop, the inflammatory process, potentially helping patients maintain their cognitive function longer,” Mike Rizzo, a graduate student in toxicology, said.

According to Kaminski, the patients who didn’t smoke cannabis had a very high level of inflammatory cells compared to those who did use it.

“Those who used marijuana had levels pretty close to a healthy person not infected with HIV,” Kaminski said.

Kaminski’s lab was the first to identify the proteins that bind cannabis compounds on the surface of immune cells. Up until then, it was unclear how these compounds affected the immune system.

“We’ll continue investigating these cells and how they interact and cause inflammation specifically in the brain,” Rizzo said. “What we learn from this could also have implications to other brain-related diseases like Alzheimer’s and Parkinson’s since the same inflammatory cells have been found to be involved.”