(p. 774) Depersonalization disorder 

Depersonalization, a term coined by Dugas in 1898, is defined in DSM-IV as ‘an alteration in the experience of self so that one feels detached from and as if one is an outside observer of one's outside mental processes or body’. Brief, self-limiting experiences of depersonalization commonly occur in healthy people in the context of fatigue, intense stress, or during/after intoxication with alcohol or illicit drugs. However, some people experience chronic depersonalization of a disturbing intensity, causing significant distress and impacting on quality-of-life and daily functioning. This may occur as a primary depersonalization disorder (DPD), or in the context of other psychiatric or neurological conditions. In this chapter, we consider the primary disorder, although some sections are also relevant to secondary depersonalization. The depersonalization experience is one of feeling strangely altered and unreal, in a way that sufferers often find very hard to convey. It is often accompanied by the related phenomenon of derealization, in which the person's surroundings are experienced as somehow remote and lacking immediacy and vibrancy, as if the world itself has become oddly unreal. Patients with persistent depersonalization and derealization often use the analogy of feeling as if they are on the set of a play or film, where nothing is real and they are acting out a role rather than living a real life.