This is a song about a girl who has insanity problems, probably caused by drugs. She's going mad and this "Disturbia" just came out of her head, a place/disease where she can't escape out of whatever she does. There are a lot of questions she can't find the answers and makes her drown in confusion.
This song is so amazing. Whoever wrote it was a genius and it was even better 'coz it's Rihanna who's singing it. This song is perfectly written, sung, and played. The tune makes a scary appeal to the listeners and still it makes you wanna party.