APA Dictionary of Psychology

a dissociative disorder characterized by persistent or recurrent episodes of depersonalization and/or derealization, in which individuals feel detached from themselves, their mental processes, or their surroundings, while reality testing remains intact. Symptoms cause significant distress or impair social, occupational, or other areas of functioning; may occur episodically or chronically; and onset can be acute. Depersonalization/derealization disorder can be associated with anxiety, panic, trauma exposure, or sleep deprivation, with symptoms occurring during or shortly after the exposure.