Marijuana is well known for causing psychosis, paranoia, panic, and other disturbed mental states. There's a reason they tell you not to eat the whole brownie - once the bad trip comes on, you're stuck with it and just have to ride it out. It can be quite harrowing. I also don't think marijuana is at all safe to take regularly, just looking at people who do so. It seems to incur actual neurological changes - you even stop having dreams. I understand that it can be fun, but all things must be taken with moderation, and people's increasing obsession with this psychoactive drug is worrisome.