Dissociative identity disorder (DID), also known as multiple personality disorder, is a condition characterized by two or more distinct personalities or identities that control a person's behavior. The personalities are called alters and each has their own way of interacting. To be diagnosed with DID, a person must experience memory loss beyond normal forgetfulness and have at least two personalities routinely take control of their behavior. There are several approaches to explaining and understanding DID, including that it develops as a defense mechanism for children experiencing trauma, like abuse, and that each alter has their own traits and way of responding to situations. However, there is no consensus on the cause and effective treatments are still being explored.