The most common form of dissociation hysteria is

Dissociative Amnesia This is the commonest clinical type of dissociative disorder. Occurring mostly in adolescent and young adults (females more than males, except in war), it is characterised by a sudden inability to recall impoant personal information (amnesia), paicularly concerning stressful or traumatic life events. The amnesia cannot be explained by everyday forgetfulness and there is no evidence of an underlying medical illness. Ref: A Sho Textbook of Psychiatry, Niraj Ahuja, 7th Edition, pg. no. 100