Depersonalization

"The experience of depersonalization involves an alteration in the individual's sense of self so that the person feels unreal as if he or she were in a dream, like a machine, dead, self-estranged, or otherwise significantly changed from his or her normal state.  Sensory distrubances such as anethesias, parasthesias, alterations in sense of body size or body parts, macroscopia or microscopia or the experience of being outside of one's body and watching ones self from a distance or looking down from above are often present....
No single explanation accounts for the widespread nature of feelings of depersonalization, which are present in about 15 - 30% of all psychiatric patients irrespective of diagnosis.  Nevertheless, as documented earlier in this chapter, depersonalization syndromes are frequently associated with a history of sustained traumas....
Dizziness or fainting episodes are frequently associated with onset of depersonalization syndromes..."

from the book "Diagnosis & Treatment of Multiple Personality Disorder" - Frank W. Putnam