A friend of Brad Pitt's said that he "convinced Angelina to go see a doctor because he was afraid something was very wrong with her. She doesn't have much of an appetite and is eating very little. Tests were run and Brad's family were led to believe that her illness might be something like hepatitis, but since then he's clammed up, I think he knows what's wrong, but he's keeping it from people."
It was reported that Jolie is undergoing drug treatment, but drugs lead her to extreme emotions, which influenced the relationship between her and partner Brad Pitt.
Source: Xinhua & Sociliate's Life