No, cannabis doesn't kill hoards of brain cells. It just kind of, slows them down, the whole function of the brain and brain cells slow down. But breathing ooutside air in kills hundreds of braincells. Taking a shower or shitting kills brain cells. The more we age, the more our brains slow down and die. Everyday your brain dies a little. That's why so many old people are in homes because thorughout their life, like ours, brain cells just die off naturally.

Nothing to be alarmed about though. As long as you can support yourself and live a life of your own, then you should be allowed to smoke it, but that's another story.