<unk>  is an alteration in the perception of the external world, causing sufferers to perceive it as unreal, distant, distorted or falsified. Other symptoms include feeling as if one's environment is lacking in spontaneity, emotional coloring, and depth. It is a dissociative symptom that may appear in moments of severe stress.<unk>  is a subjective experience pertaining to a person's perception of the outside world, while depersonalization is a related symptom characterized by dissociation towards one's own body and mental processes. The two are commonly experienced in conjunction with one another, but are also known to occur independently. Chronic<unk>  is fairly rare, and may be caused by occipital–temporal dysfunction. Experiencing<unk>  for long periods of time or having recurring episodes can be indicative of many psychological disorders, and can cause significant distress among sufferers. However, temporary<unk>  symptoms are commonly experienced by the general population a few times throughout their lives, with a lifetime prevalence of up to 26-74% and a prevalence of 31–66% at the time of a traumatic event.
Derealization
Body substance isolation
Rejuvenation
Jactitation 
Depurination
Semantic satiation
Disinhibition
Marsupialization