I think the real reason for your neighbot to go dumb is not only his smoking habits, but lack of excersize he’s applying to his brain. I know for sure that it does not make you any dumber than you already are, or willing to be. I know many great thinkers and generally smart people using pot and it doesn’t effect them as it effects less educated people. I think people should be able to chose how they live their lives. Noone is responsible or should be concerned about others mental state.