I just watched Mario Bava's SHOCK (1977) on TCM-dam-Bava did some sick s**t-but this movie goes all out...I mean-a little 8 year old kid has a hard on for his own mother because he's possessed by his dead father-who was a junkie!
Heres the trailer-it's in italian-I saw a dubbed version. It's creepy as hell.
If you get a chance to see this movie-do so-but! WARNING!-this is NOT a movie to watch with your children-it is f**ked up!