This article is from the Dissociation FAQ, by Discord (firstname.lastname@example.org) with numerous contributions by others.
Psychogenic Fugue is the assumption of a new identity and the inability to
recall one's previous identity; it involves a complete switch in
lifestyle, including home and/or work recall. This is usually caused by
severe psychosocial stress, such as severe marital problems, being a
part of military conflict, or being in some type of natural disaster.
Psychogenic Amnesia is a sudden inability to recall important personal
information, when not due to any organic cause. Like Psychogenic Fugue,
this is usually caused by severe psychosocial stress
Both psychogenic fugue and psychogenic amnesia are sudden, and they both
are usually fairly short-lived, with a complete recovery made. They are
most common during wartime or just after a natural disaster.
Differential Diagnoses include epilepsy and other forms of amnesia; both
are also sometimes feigned (malingering).