Textbook of Psychiatry/Dissociative Disorders/Phenomenology

Epidemiology
Several studies have shown that dissociative disorders may have been previously under diagnosed and a much higher prevalence is encountered. (Foote et al. 2006) The prevalence of dissociative disorders in general psychiatric settings ranges between 5.0% and 20.7% among inpatients (Sar et al. 2007) and between 12.0% and 29.0% among outpatients. (Sar et al. 2007) In an outpatient study (the only methodologically strong outpatient study) in Turkish outpatients Sar et al. found that 12% of Turkish outpatients could qualify for a diagnosis of a dissociative disorder, including 4% with dissociative identity disorder and 8% with dissociative disorder not otherwise specified. (Foote et al. 2006) Only 1% of those patients had been diagnosed with dissociative disorder before entering the study. (Foote et al. 2006) Inpatient populations have been studied more thoroughly as listed in Table 1. (Foote et al. 2006) In one of the studies, frequency of dissociative disorders was studied in the psychiatry emergency ward and noted to be as high as 34.9%. (Sar et al. 2006)

'''Table 1. Studies of the prevalence of dissociative disorders in inpatient psychiatric patients'''

Clinical Symptoms and Classification
In International Classification of Diseases, 10th revision (ICD-10) dissociative disorders has been listed under the category of Neurotic, stress- related and somatoform disorders. It includes conversion, hysteria and hysterical psychosis and excludes malingering. As per ICD-10, in dissociative disorders there is a partial or complete loss of the normal integration between memories of the past, awareness of identity and immediate sensations, and control of bodily movements. They are presumed to be psychogenic in origin, being associated closely in time with traumatic events, insoluble and intolerable problems, or disturbed relationships. The symptoms cannot be attributed to any medical or neurological disorder excluded by physical exam and investigations. In addition, there is evidence that the loss of function is an expression of emotional conflicts or needs.

'''Table 2. Classification and clinical symptoms of dissociative disorders (F44) as per ICD-10 criteria'''

The DSM-IV-TR talks about dissociative amnesia and fugue as part of dissociative disorders as included in the ICD-10 criteria but conversion disorder is a part of Somatoform disorders rather than dissociative disorders in the DSM-IV. Dissociative stupor, trance, convulsions, Ganser syndrome and motor disorders are all grouped together under Dissociative disorder NOS rather than being classified separately as in ICD-10. Dissociative Identity disorder, formerly known as multiple personality disorder is sub-classified as a part of "Other dissociative disorders" in ICD-10 whereas it has been classified separately in the DSM-IV. The American Psychiatric Association’s DSM-IV recognizes dissociative disorders as official diagnostic category; by contrast World Health Organization’s ICD-10 is more skeptical classifying dissociative disorders as conversion disorders and suggesting the dissociative identity disorder may be "a culture-specific or even iatrogenic condition." (Lalonde et al. 2001) No matter what the differences are in the classification, the overall suggestibility of the symptoms and signs are the same and the same methods of assessment may be used to diagnose dissociative disorders.

Assessment
The first step is to do a detailed clinical interview including questions about significant childhood and adult trauma. Clinicians should use careful clinical judgment about how much detail of traumatic experiences to pursue during initial interviews, especially when those experiences seem to be poorly or incompletely remembered. A premature trauma anamnesis may evoke a florid decompensation (Chu et al. 2005). The patient should be asked about episodes of amnesia, fugue, depersonalization, derealization, identity confusion, and identity alteration, age regressions, autohypnotic experiences, hearing voices, passive-influence symptoms such as "made" thoughts, emotions, or behaviors and somatoform symptoms such as bodily sensations related to past trauma (Chu et al. 2005).

Measures of Dissociation
There are three classes of instruments that assess dissociation:

Clinician-administered structured interviews, clinician-administered measures, and self-report instruments (Chu et al. 2005).

Clinician-administered structured interviews
The Structured Clinical Interview for DSM-IV Dissociative Disorders-Revised (SCID-D-R) (Bremner et al. 1993) is a 277-item interview that assesses five symptoms of dissociation: amnesia, depersonalization, derealization, identity confusion, and identity alteration. The SCID-D-R has good-to-excellent reliability and discriminant validity.

The Dissociative Disorder Interview Schedule (DDIS) is a 132-item structured interview with a yes/no format that assesses the symptoms of the five DSM-IV dissociative disorders, somatization disorder, borderline personality disorder, and major depressive disorder. The DDIS also assesses substance abuse, Schneiderian first-rank symptoms, trance, childhood abuse, secondary features of Dissociative Identity Disorder, and supernatural/paranormal experiences.

Clinician Administered Measures
The Clinician Administered Dissociative States Scale (CADSS) (Bremner et al. 1998) has 27 items with 19 subject-rated items and 8 observer-scored items, all rated on a 0-4 scale. It has three factors that assess symptoms of amnesia, depersonalization and derealization.

Self-Report Instruments
There are six self-report measures of dissociation that have been used with some frequency (Chu et al. 2005): the Dissociative Experiences Scale [DES], the Questionnaire of Experiences of Dissociation [QED], the Dissociation Questionnaire [DIS-Q], Somatoform Dissociation Questionnaire [SDQ] and the Multiscale Dissociation Inventory [MDI])

Dissociative Experiences Scale (DES, Bernstein and Putnam, 1989)

The Dissociative Experiences Scale is a widely used 28-item self-report measure for assessment of specific dissociative experiences (Bernstein et al. 1986, Carlson et al. 1993).Items are rated on a continuous scale (original version) or on an11-point Likert scale (revised version) that ranges from 0 ("never") to100 ("always"). DES items primarily tap absorption, imaginative involvement, depersonalization, derealization, and amnesia (Chu et al. 2005).

The Questionnaire of Experiences of Dissociation (QED; Riley, 1988) is a 26-item, true/false self-report instrument-not very frequently used (Chu et al. 2005).

The Dissociation Questionnaire (DIS-Q; Vanderlinden, Van Dyck,Vandereycken, Vetommen, & Verkes, 1993; Vanderlinden, 1993) is a 63-item, five-point Likert format, self-report instrument-commonly used in Europe (Chu et al. 2005).

The Somatoform Dissociation Questionnaire-20 (SDQ-20) is a 20-item self-report instrument using a five-point Likert scale (Nijenhuis, Spinhoven,Van Dyck, Van der Hart, & Vanderlinden, 1996). The SDQ-20 is explicitly conceptualized as a measure of somatoform dissociation.

The Multidimensional Inventory of Dissociation (MID) is a 218-item self-report, multiscale measure of pathological dissociation that makes diagnoses and yields a comprehensive dissociative profile (Dell, 2004). The MID is the only measure of dissociation that has validity scales: Defensiveness, Rare Symptoms, Attention-Seeking Behavior, Factitious Behavior, and Neurotic Suffering (Chu et al. 2005)

The Multiscale Dissociation Inventory (MDI; Briere, 2002) is a 30-item multiscale measure of dissociation with a 5-point Likert format. The MDI is fully standardized, allowing t score comparisons to anormative group of trauma-exposed men and women. It yields six subscales–Disengagement, Depersonalization, Derealization, Emotional Constriction/Numbing, Memory Disturbance, and Identity Dissociation–and a total dissociation scale (Chu et al. 2005).

Other Psychological Tests
Along with more specific diagnostic testing (e.g., SCID-D-R, DES, etc.), standardized psychological tests (MMPI-2, Rorschach etc.) may aid the clinician in differential diagnosis and prognosis, the identification of co-morbid disorders, and the evaluation of treatment options (Chu et al. 2005).

Special investigations
No specific investigations are specific to Dissociative disorders. In one study, MRI revealed the amygdalar and hippocampal volumes to be smaller in females with Dissociative identity compared to healthy subjects (Vermetten et al. 2006). But the use of such expensive studies such as MRI is questionable to diagnose dissociative disorders, also when this finding is not specific to dissociative disorders. In another study it was documented that low serum lipid levels may be related to a high incidence of self-injurious behaviors and borderline features in patients with dissociative disorders (Agargun et al. 2004).

Other rating scales that are available for use to assess Dissociative disorders (http://www.neurotransmitter.net/dissociationscales.html)
Diagnostic Drawing Series (DDS) (Mills & Cohen, 1993 Adolescent Dissociative Experiences Scale-II (A-DES) Child Dissociative Checklist (CDC), Version 3 Peritraumatic Dissociative Experiences Questionnaire (PDEQ) Cambridge Depersonalization Scale Steinberg Depersonalization Questionnaire Adolescent MID 6.0 Dissociative Features Profile (DFP)