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Could a chemical in pot help protect against Alzheimer's disease?

Early lab findings suggest that the same chemical in marijuana that gives people a high may be worth exploring more as a possible treatment for Alzheimer's disease, CBS San Francisco reports. But it's far from ready to be used as a prevention or treatment option, experts say.

Scientists at the Salk Institute have found evidence that tetrahydrocannabinol, or THC, the active ingredient in pot, reduces amyloid beta in nerve cells; amyloid beta is the toxic protein in the brain associated with Alzheimer's. Their study is published in the journal Nature.

Alzheimer's, an incurable brain disease that results in memory loss and death, affects more than 5 million Americans, according to the Alzheimer's Association.

Plaque-forming amyloid beta proteins in the aging brain are a hallmark of the disease, along with cellular inflammation and neuron death.

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The brain's natural defense against amyloid beta is the production of endocannabinoid receptors. Physical activity helps activate those receptors, but the scientists found the psychoactive effects of THC mimic that process in the lab.

"When we were able to identify the molecular basis of the inflammatory response to amyloid beta, it became clear that THC-like compounds that the nerve cells make themselves may be involved in protecting the cells from dying," said researcher and co-author Antonio Currais in a press release.

"Although other studies have offered evidence that cannabinoids might be neuroprotective against the symptoms of Alzheimer's, we believe our study is the first to demonstrate that cannabinoids affect both inflammation and amyloid beta accumulation in nerve cells," said Salk professor David Schubert, the senior author of the paper.

The positive results, observed on lab-grown human neurons treated with THC-like compounds to reduce inflammation and prevent cell death, have powerful implications. The Alzheimer's researchers believe it signals a potential avenue for preventing neurological damage from this devastating disease.

Schubert notes that the evidence of the value of THC in the fight against Alzheimer's disease has, so far, been limited to exploratory laboratory models. It has not yet been tested in people in a clinical trial to determine what effects it may have on human health.

Heather Snyder, Ph.D., Senior Director of Medical and Scientific Operations at the Alzheimer's Association, told CBS News, "It's an interesting study, but it's very early -- in cells, in a dish, in a lab. How that translates to an animal model or a human, there are a lot of steps in that process still."

She said, "The paper nicely outlines from a basic science perspective a particular pathway."

And while the findings don't give any information about potential therapies and interventions for people living with Alzheimer's now, Snyder said, "It gives us potential targets that should be explored."

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"This is so preliminary," agreed Scott Krakower, an assistant unit chief of psychiatry at Zucker Hillside Hospital in New Hyde Park, New York. Krakower was not involved in the study but has a background in neuroscience lab work in this area.

He said the potential impact of THC on Alzheimer's is a complicated question to explore because the end goal would have to be finding a way to develop a drug that would offer any potential medical benefit but without the more toxic effects of marijuana.

"It may be a little protective. That may be true. But we also know there's a neurotoxic effect with THC, especially in large quantities," Krakower told CBS News.

He said these findings are very early and people shouldn't take the results and assume it's safe or effective to use marijuana to fend off Alzheimer's. It could be especially dangerous in those who already have Alzheimer's.

According to the Alzheimer's Association, people with dementia are at risk for experiencing psychotic symptoms during the course of their disease due to changes in how their brains process and retrieve new information.

"People with Alzheimer's may read this and think it's okay to smoke weed but that may make their psychosis even worse," said Krakower. "It's a big part of the illness. They often get terrible hallucinations.

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