Psychiatric interest in the human response to overwhelming psychological trauma has waxed and waned over the past century. Both Janet (1889) and Freud (1920) were deeply interested in the lasting psychological damage resulting from uncontrollably terrifying events, particularly those occurring early in the life-cycle, and both attributed many features of adult psychopathology to early traumatic life events. After Freud concluded that hysterical symptoms were not due to actual childhood trauma, but to intrapsychic elaborations of childhood fantasies, the role of trauma was abandoned as a central focus of psychiatric investigations. The more recent shift in psychiatric focus to a biomedical model has emphasized the investigation of biological and hereditary determinants of mental illness, again at the exclusion of the rol~ of actual life events as determinants of mental illness. Current biological approaches to mental illness tend to be founded in the assumption that biological aspects of psychological phenomena are necessarily genetically based. This assumption excludes the overwhelming evidence that the central nervous system exists in a constant interplay with the environment and continues to some degree to be shaped by it throughout life, particularly during the first decade of life, when biological and cognitive functions mature in concert with the social surrounding (van der Kolk, 1986).