Epidemiology of Dissociative Disorders: An Overview
Epidemiology Research International
Volume 2011 (2011), Article ID 404538, 8 pages
Vedat Sar Department of Psychiatry, Istanbul Faculty of Medicine, Istanbul University, 34390 Capa, Istanbul, Turkey
….screening studies using diagnostic tools designed to assess dissociative disorders yielded lifetime prevalence rates around 10% in clinical populations and in the community. Special populations such as psychiatric emergency ward applicants, drug addicts, and women in prostitution demonstrated the highest rates. Data derived from epidemiological studies also support clinical findings about the relationship between childhood adverse experiences and dissociative disorders.
…. Data collected in diverse geographic locations such as North America , Puerto Rico , Western Europe , Turkey , and Australia  underline the consistency in clinical symptoms of dissociative disorders. These clinical case series have also documented that dissociative patients report highest frequencies of childhood psychological trauma among all psychiatric disorders. Childhood sexual (57.1%–90.2%), emotional (57.1%), and physical (62.9%–82.4%) abuse and neglect (62.9%) are among them.
….Two studies in North America demonstrated that 13.0–20.7 % of psychiatric inpatients had a dissociative disorder [22, 23]. Studies on dissociative disorders in Istanbul, Turkey, yielded a prevalence slightly above 10% among psychiatric inpatients and outpatients [8, 24, 25]. Although still considerable, these rates were lower in the Netherlands , Germany , and Switzerland  among inpatients, that is, between 4.3%–8.0%. A Finnish study  reported higher rates for psychiatric outpatients (14.0%) and inpatients (21.0%). Emergency admissions of a university psychiatric clinic in Istanbul, Turkey yielded the highest rate in the country: 35.7% . In a study from Zurich, Switzerland, among severely impaired psychiatric outpatients, prevalence of all dissociative disorders were 25.0% .
….Overall, the prevalence of dissociative disorders in inpatient and outpatient psychiatric settings seems to be around 10%, while approximately half of them (5%) has DID, the most severe type of dissociative disorders.
…. A screening study on a representative sample…in Manitoba, Canada, using the DDIS yielded 11.2% prevalence for all DSM-III-R dissociative disorders . Two large-scale studies were conducted in the general population of Sivas City, Turkey, supported these findings gathered in North America. The first one was conducted on a representative sample of 994 participants from both genders . Approximately 3/4 of the probands dropped-out who were selected for a second and third diagnostic interview due to their elevated DES scores. Despite of this high loss in data, 0.4% of the original sample was diagnosed as having clinically confirmed DID. The second study in Sivas City, Turkey was conducted on a representative female sample of 648 participants in the same city using a structured diagnostic interview, that is, the DDIS . The overall prevalence of dissociative disorders was 18.3%. 1.1% of the population had DID. However, the largest group was DDNOS (8.3%). Conditions based primarily on the presence of distinct personality states (i.e., DID and DDNOS-1) built up a prevalence of 5.2% for chronic complex dissociative disorders.
….In a recent North American study conducted in the community (New York,…the prevalence was 8.6% for all DSM-IV dissociative disorders observed in the past year ….A further study  documented that 6.3% of the general population suffered from three or more frequently occurring dissociative symptoms possibly representing a dissociative disorder. In The Netherlands, 378 subjects from a non-clinical population were screened using the dissociation questionnaire (DIS-Q), a self-rating scale of European origin [43, 44]. 2.1% of the participants had a score above the cutoff point (score of 2.5), and 0.5 % had a score comparable to those of patients with dissociative disorders (scores of 3.0 or higher).
….Among consecutive inpatients admitted to a dependency treatment unit of a large state mental hospital in Istanbul, Turkey, the lifetime prevalence of DSM-IV dissociative disorders was 17.2% . These rates were 9.0% for alcohol dependency only  and 26.0% for patients with chemical dependency . Those rates were between 15.0% and 39.0% [48–50] for patients with chemical dependency in North America.
….In Germany, a screening study was conducted on 51 male criminal offenders admitted to a medicolegal institution by the court so as to understand diminished or lack of responsibility for the offence due to psychiatric disorder, including a large group of persons with substance-use disorders . Using the SCID-D, a high prevalence of dissociative symptoms and disorders (23.5%), mostly DDNOS, was demonstrated. 22.6% of the group had a DES score 20.0 or higher. In Turkey , 26.8% of 108 male prisoners in a regular correctional center had a DES score 20 or above. This rate was 18.5% for DES scores 30 or above which is known to be the cut-off level for chronic dissociative disorders . Nevertheless, according to the SCID-D, 15.7% of the subjects had a dissociative disorder, that is, either DDNOS or dissociative amnesia. Exotic dancers and women in prostitution have also been demonstrated as risk groups for dissociative disorders [52–55, 59]. This seem to be due to the highly traumatic background of the probands.
….Epidemiological studies also documented the relationship between dissociative disorders and childhood trauma, an association clinicians and researchers are familiar with [32, 71, 72]. A screening study conducted on consecutively admitted psychiatric outpatients yielded elevated rates for sexual (27.8%), physical (50.0%,), and emotional (72.2%) abuse and neglect (83.3%) among dissociative patients in comparison to nondissociative controls . In the inpatient psychiatric unit of the same institution, these rates were 58.8%, 82.4%, 70.6%, and 58.8%, respectively . Apparently, patients with childhood sexual and/or physical abuse were hospitalized more readily pointing to a more crisis-prone and severe general condition. On the other hand, dissociative outpatients and dissociative subjects identified in non-clinical settings report emotional abuse and neglect predominantly [24, 38]. Nevertheless, in a Turkish study in the community, subjects with dissociative or conversion disorder (somatic dissociation) reported significantly higher levels of childhood traumata than the remaining participants [38, 69]. In a case series and also in the community, conversion disorder patients with a concurrent dissociative disorder reported childhood traumata more frequently than those without.