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Diagnosis od depersonalization disorder is based on the self-reported experiences of the person followed by a clinical assessment.
Psychiatric assessment includes a psychiatric history and some form of mental status examination. Since some medical and psychiatric conditions mimic the symptoms of DPD, clinicians must differentiate between and rule out the following to establish a precise diagnosis: temporal lobe epilepsy, panic disorder, acute stress disorder, schizophrenia, migraine, drug use, brain tumour or lesion. No laboratory test for depersonalization disorder currently exists.
The diagnosis of DPD can be made with the use of the following interviews and scales:
The Structured Clinical Interview for DSM-IV Dissociative Disorders (SCID-D) is widely used, especially in research settings. This interview takes about 30 minutes to 1.5 hours, depending on individual's experiences.
The Dissociative Experiences Scale (DES) is a simple, quick, self-administered questionnaire that has been widely used to measure dissociative symptoms. It has been used in hundreds of dissociative studies, and can detect depersonalization and derealization experiences.
The Dissociative Disorders Interview Schedule (DDIS) is a highly structured interview which makes DSM-IV diagnoses of somatization disorder, borderline personality disorder and major depressive disorder, as well as all the dissociative disorders. It inquires about positive symptoms of schizophrenia, secondary features of dissociative identity disorder, extrasensory experiences, substance abuse and other items relevant to the dissociative disorders. The DDIS can usually be administered in 30–45 minutes.
The Cambridge Depersonalization Scale (CDS) is a method for determining the severity of depersonalization disorder patients may suffer from. It has been proven and accepted as a valid tool for the diagnosis of depersonalization disorder in a clinical setting. It was validated through trials with a sample of patients who had been confirmed to be suffering from depersonalization disorder. It is also used in a clinical setting to differentiate minor episodes of depersonalization from suffering from actual symptoms of the disorder. Due to the success of the CDS, a group of Japanese researchers underwent the effort to translate the CDS into the J-CDS or the Japanese Cambridge Depersonalization Scale. Through clinical trials the Japanese research team successfully tested their scale and determined its accuracy. They did discover a limitation that the scale did not allow for the differentiation between past and present episodes of depersonalization. It should also be noted that it may be difficult for the patient to describe the duration of depersonalization episodes and thus the scale lacks some degree of accuracy. The project was conducted in the hope that it would stimulate further scientific investigations into depersonalization disorder.
Depersonalization disorder is classified differently in the DSM-IV-TR and in the ICD-10: In the DSM-IV-TR this disorder it is seen as a dissociative disorder; in the ICD-10 as an independent neurotic disorder. Whether depersonalization disorder should be characterized as a dissociative disorder can be discussed; it relies very much upon how dissociative is being described.
The diagnostic criteria defined in section 300.6 of the Diagnostic and Statistical Manual of Mental Disorders are as follows:
- Longstanding or recurring feelings of being detached from one's mental processes or body, as if one is observing them from the outside or in a dream.
- Reality testing is unimpaired during depersonalization
- Depersonalization causes significant difficulties or distress at work, or social and other important areas of life functioning.
- Depersonalization does not only occur while the individual is experiencing another mental disorder, and is not associated with substance use or a medical illness.
The DSM-IV-TR specifically recognizes three possible additional features of depersonalization disorder:
- Derealization, experiencing the external world as strange or unreal.
- Macropsia or micropsia, an alteration in the perception of object size or shape.
- A sense that other people seem unfamiliar or mechanical.
Dissociation is defined as a "disruption in the usually integrated functions of consciousness, memory, identity and perception, leading to a fragmentation of the coherence, unity and continuity of the sense of self. Depersonalisation is a particular type of dissociation involving a disrupted integration of self-perceptions with the sense of self, so that individuals experiencing depersonalisation are in a subjective state of feeling estranged, detached or disconnected from their own being."
In ICD-10, this disorder is called depersonalization-derealization syndrome F48.1. The diagnostic criteria are as follows:
- 1. one of the following:
- depersonalization symptoms, i.e. the individual feels that his or her feelings and/or experiences are detached, distant, etc.
- derealization symptoms, i.e. objects, people, and/or surroundings seem unreal, distant, artificial, colourless, lifeless, etc.
- 2. an acceptance that this is a subjective and spontaneous change, not imposed by outside forces or other people (i.e. insight)
The diagnosis should not be given in certain specified conditions, for instance when intoxicated by alcohol or drugs, or together with schizophrenia, mood disorders and anxiety disorders.
Some disorders have similar symptoms. The clinicians, must differentiate between and rule out the following disorders to establish a precise diagnosis.
- Temporal Lobe Seizures ( epilepsy )
- Atypical forms of migraine and headache
- Panic disorder
- Acute stress disorder
- Drug abuse
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