The authors define depersonalization as an altered awareness of the self such that the individual feels strange or unreal. They then add a cluster of affects such as loss of emotion, sense of detachment, and altered perception of time and space to describe a depersonalization syndrome which they feel to be a relatively nonspecific accompaniment of various disorders. They refer to previous studies that point to depersonalization as a specific response to extreme danger. This issue was studied in a group of individuals who were hospitalized following automobile accidents and compared with a group of psychiatric patients. The method involved a questionnaire technique. It demonstrated the transient development of a depersonalization syndrome in a substantial portion of persons exposed to life-threatening danger. An associated group of reactions indicating heightened arousal and alertness was also found to be present. This led to the hypothesis that depersonalization may represent an adaptive mechanism which both intensifies alertness and dampens potentially disorganizing emotion.