Cannabis has been proven to cause NO form of cancer in ANY living cell on this earth. It has also been proven to NOT kill any brain cells. The only cell's it kills in the body are called Glioma cells which are the only ones to turn cancerous in the brain. They are not used by the brain either.

Cannabis can possibly prolong the life of a cell, therefore possibly increasing the life of a cannabis user. *This is no proven, but it is proven to work on mice*

Cannabis is 100% harmless. you could have a THC drip in your arm your whole life and never die.