At last… evidence that smoking pot does NOT kill braincells:

Marijuana may help stave off Alzheimer’s - Alzheimer’s Disease - MSNBC.com
WASHINGTON - Good news for aging hippies: smoking pot may stave off Alzheimer’s disease.

New research shows that the active ingredient in marijuana may prevent the progression of the disease by preserving levels of an important neurotransmitter that allows the brain to function.

Researchers at the Scripps Research Institute in California found that marijuana’s active ingredient, delta-9-tetrahydrocannabinol, or THC, can prevent the neurotransmitter acetylcholine from breaking down more effectively than commercially marketed drugs.