Actually THC, cannabidiol, and most of the other cannabiniods in cannabis, if not all, are neuroprotective antioxidants. The National Institutes of Health states this in a 2007 research paper, as do various other research papers. Alcohol will kill brain cells, and cannabis can help to protect your brain cells from such damage. If anything in cannabis kills brain cells, it would be the carbon monoxide from burning it, but most people don't burn much, and cigarette smoking will of course produce much more carbon monoxide, as tobacco smokers need to smoke a lot more. Car engine exhaust is probably much more dangerous as well.

http://boards.cannabis.com/medicinal...ioxidants.html