You smoking pot and having thoughts about your parents dying isn't in any way related to the possibility that they might actually be dying. What's it got to do with pot? Probably it just intensifies the deep seeded feelings associated with death. I don't think that's anything to shy away from; you've just got to keep your wits about it and try to maintain some composure. As for ghosts... Shit, man, everyone is terrified of ghosts. That's not abnormal. I can barely sleep at night.