depersonalization disorder
a dissociative disorder characterized by one or more episodes of depersonalization severe enough to impair social and occupational functioning. Onset of depersonalization is rapid and usually manifested in a sensation of self-estrangement, a feeling that one’s extremities are changed in size, a sense of being mechanical, a perception of oneself as if from a distance, and, in some cases, a feeling that the external world is unreal (derealization).