You haven't studied the effect of pot much, I take it?

It's linked to schizophrenia. Once in your system it can take a month to dissipate, but it doesn't diminish it just builds up like a game of Tetris. It makes people paranoid. It's drawn deeper into the lungs and therefore does have a serious risk of causing lung cancer, even if it doesn't have as many chemicals as the shop-bought cigarettes do.