a personality disorder (= a mental condition affecting a person's relationships, and their idea of themselves and what is around them) in which a person's mood often changes suddenly and they have difficulty controlling their behaviour or forming long relationships

He was diagnosed with borderline personality disorder. 他被诊断出患有边缘性人格障碍症。

Her lawyers presented evidence that she suffered from a borderline personality disorder. 她的律师提供了证据，证明她患有边缘性人格障碍症。