Dissociative amnesia is a type of psychological amnesia in that it is not caused by damage to the brain itself. Patients with the disorder are not able to recall details about themselves. All or some self-knowledge appears to have become non-recallable. The personal information that cannot be recalled is often traumatic or stressful to the patient. Patients are however able to form new memories, therefore the amnesia is retrograde only. The amnesia can take on the form of the inability to recall memories about a specific situation, or it can be more widespread where patients are unable to recall self-knowledge stretching back years. In these cases patients are often discovered wandering with no idea who they are.