A disorder characterized by a retrospective gap in memory of important personal information, usually of a traumatic or stressful nature; the memory loss far exceeds ordinary forgetfulness and is not the result of substance use or the consequence of a medical condition.

Dissociative amnesia or psychogenic amnesia is a dissociative disorder "characterized by retrospectively reported memory gaps. These gaps involve an inability to recall personal information, usually of a traumatic or stressful nature." The concept is scientifically controversial and remains disputed. Dissociative amnesia was previously known as psychogenic amnesia, a memory disorder, which was characterized by sudden retrograde episodic memory loss, said to occur for a period of time ranging from hours to years to decades. The atypical clinical syndrome of the memory disorder (as opposed to organic amnesia) is that a person with psychogenic amnesia is profoundly unable to remember personal information about themselves; there is a lack of conscious self-knowledge which affects even simple self-knowledge, such as who they are...