Awareness of the role of psychological trauma in the genesis of a variety of psychiatric problems has waxed and waned throughout the history of psychiatry. Although the traumatic memories that haunt people after experiencing overwhelming terror have always been a central theme in literature, psychiatry has suffered periodically from marked amnesias in which well-established knowledge was forgotten abruptly, and the psychological impact of man's inhumanity to man was ascribed to constitutional or intra-psychic factors alone.