Speaking to New magazine, the Twilight star revealed that he endures mood swings and that he believes he suffers from bipolar disorder.
"You over-analyse everything - you analyse how if you say one thing, someone likes you, and if you say another, they don't," the 24-year-old said.
He added: "You begin to experiment on people, which isn't good for real life. I don't think I'm very romantic any more - just manic depressive."