The active ingredient of marijuana could be considerably better at suppressing the abnormal clumping of malformed proteins that is a hallmark of Alzheimer's than any currently approved drugs prescribed for the treatment of the disease.

Scientists report the finding in the Oct. 2 issue of the journal Molecular Pharmaceutics.

About 4.5 million Americans suffer from Alzheimer's disease, which gradually destroys memory. As more people survive into old age, cases of Alzheimer’s disease are expected to triple over the next 50 years. There is no known cure.

The researchers looked at THC, the compound inside marijuana responsible for its action on the brain. Computer models suggested THC might inhibit an enzyme with the tongue-twisting name of acetylcholinesterase (also called AChE) that is linked with Alzheimer's.

AChE is known to help accelerate the formation of abnormal protein clumps in the brain known as amyloid plaques during Alzheimer's. This enzyme also helps break down the brain chemical acetylcholine, which is linked to memory and learning. Acetylcholine levels are reduced during Alzheimer's.

In lab experiments, the scientists found THC was significantly better at disrupting the abnormal clumping of malformed proteins. THC could completely prevent AChE from forming amyloid plaques, while two drugs approved for use against Alzheimer's, donepezil and tacrine, reduced clumping by only 22 and 7 percent, respectively, at twice the concentration of THC used in the tests.

"We're not advocating smoking dope, but if we can make analogues of THC, it could play a role in treating Alzheimer's," researcher Kim Janda, a chemist at the Scripps Research Institute in La Jolla, Calif., told LiveScience. "It would be nice to do more animal studies along these lines."

Past research on human brain tissues and experiments with rats have suggested that synthetic analogues of THC can reduce the inflammation and prevent the mental decline associated with Alzheimer's disease.

However, marijuana is not necessarily good for the mind. Prior investigations have shown that years of heavy marijuana use, consisting of four or more joints a week, can impair memory, decision making, and the ability to pay attention to more than one thing at a time.