Depersonalization, a term coined by Dugas in 1898,⁽¹⁾ 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.

The diagnosis requires the presence of persistent, distressing depersonalization and/or derealization, occurring in clear consciousness, and not due to another disorder or substance. Some patients find it impossible to divide their symptoms into depersonalization and derealization, seeing them as essentially two ways of describing the same experience. Nevertheless, one may encounter patients who describe one without the other. ‘Pure’ derealization is, however, uncommon.

In addition, there are a number of other symptoms that occur with sufficient frequency to be considered as part of the depersonalization syndrome, although their presence is not essential for making the diagnosis. These are as follows:

Desomatization—a loss or diminution of bodily sensation, sometimes accompanied by a feeling of disembodiment.

De-affectualization—a loss or diminution of emotional reactivity-the feeling that life has somehow been drained of emotional content, or that the sufferer feels little emotion in response to people or events that would normally be expected to elicit an emotional response. This may have significance for intimate relationships. It should be noted that de-affectualization is not usually accompanied by blunted affect of the type commonly seen in schizophrenia.

De-ideation—a feeling of mental emptiness which may cause difficulty in concentrating, a distorted experience of time, and a sense of detachment from memories. Often accompanied by a feeling of ‘stuffiness in the head’ or ‘as if my brain has turned to cotton wool’.

While ‘depersonalization’ and ‘derealization’ are well-established in the psychiatric lexicon, the three terms listed above are not widely used or discussed. However, a recent analysis of symptoms reported by patients with DPD gave strong support to the idea that the condition should be considered as a syndrome, with symptoms occurring in domains corresponding to the terms used above.⁽²⁾

In DSM-IV, DPD is classified as a dissociative disorder, while in ICD-10 it falls under the vague heading of ‘other neurotic disorders’, and is not linked to any other category of disorder.

It has been argued that DPD is not truly a dissociative disorder, as dissociation is generally characterized by a lack of subjective awareness of change, whereas in DPD the experience of feeling changed is central. However, this apparent contradiction can be resolved if dissociation is conceptualized as a category incorporating both types of phenomenon.⁽³⁾

The diagnosis should be established by a careful clinical assessment. Because DPD remains a somewhat obscure disorder, patients with this condition may have had unproductive consultations with other professionals and formed the impression that their symptoms are baffling, perhaps even unique. Being given the correct diagnosis and the opportunity to discuss it in depth with an informed psychiatrist may come as a great relief. The reassurance derived from this may in itself have a powerful therapeutic effect.

Where there are other psychiatric symptoms (e.g. anxiety, panic attacks, depressive features), the distinction between primary and secondary depersonalization may be difficult. The best way to approach this is simply to establish what the dominant symptoms are at the time of presentation. In a patient with a history of panic disorder who has developed severe unremitting depersonalization, and now has very infrequent panic attacks, the most pragmatic approach is to diagnose DPD. The fact that the panic symptoms preceded the onset of DPD is less important than the fact that it is now the DPD symptoms that dominate the clinical picture.

This issue aside, the main psychiatric differential hinges on the possibility that when patients describe feeling altered or unreal, they are articulating delusional beliefs. It is important to establish that patients have no psychotic symptoms; in particular, that they do not literally believe themselves to be unreal or dead, as this is suggestive of psychotic depression and the Cotard delusion, rather than DPD.

Depersonalization can also occur in neurological disorders, principally temporal lobe epilepsy and migraine.⁽⁴⁾ Here the history is usually of brief, stereotyped episodes, with associated features that should provide sufficient clues to the underlying diagnosis.