Enijenhuis.nl

ABSTRACT. In most of the recent scientific and clinical literature,
dissociation has been equated with dissociative amnesia, depersonaliza-
tion, derealization, and fragmentation of identity. However, according
to Pierre Janet and several World War I psychiatrists, dissociation also
pertains to a lack of integration of somatoform components of experi-
ence, reactions, and functions. Some clinical observations and contem-
porary studies have supported this view. Somatoform dissociation, which
can be measured with the Somatoform Dissociation Questionnaire
(SDQ-20), is highly characteristic of dissociative disorder patients, and
a core feature in many patients with somatoform disorders and in a
subgroup of patients with eating disorders. It is strongly associated with
reported trauma among psychiatric patients and patients with chronic
pelvic pain presenting in medical healthcare settings. Motor inhibitions
and anesthesia/analgesia are somatoform dissociative symptoms that
are similar to animal defensive reactions to major threat and injury.
Among a wider range of somatoform dissociative symptoms, these
particular symptoms are highly characteristic of patients with dissocia-
tive disorders. The empirical findings reviewed in this article should
have implications for the contemporary conceptualization and defini-
tion of dissociation, as well as the categorization of somatoform disor-
ders in a future version of the DSM. [Article copies available for a fee from
The Haworth Document Delivery Service: 1-800-342-9678. E-mail address:
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E 2000 by The Haworth Press, Inc. All rights reserved.] KEYWORDS. Dissociation, somatoform, trauma
Ellert R. S. Nijenhuis is affiliated with Cats-Polm Institute, The Netherlands.
Address correspondence to: Ellert R. S. Nijenhuis, Cats-Polm Institute, Dobben- wal 90, 9407 AH Assen, The Netherlands (E-mail: e.nijenhuis@wxs.nl).
The author wishes to thank Kathy Steele for her assistance in preparing this Journal of Trauma & Dissociation, Vol. 1(4) 2000 E 2000 by The Haworth Press, Inc. All rights reserved.
JOURNAL OF TRAUMA & DISSOCIATION What are the major symptoms of the dissociative disorders? According to the Diagnostic and Statistical Manual for Mental Disorders, Fourth Edition(DSM-IV; American Psychiatric Association, 1994), the essential feature ofdissociation is a disruption of the normal integrative functions of conscious-ness, memory, identity, and perception of the environment. Thus, the currentstandard for the assessment of dissociative disorders, the Structural ClinicalInterview for DSM-IV Dissociative Disorders (SCID-D; Steinberg, 1994),includes four symptom clusters: dissociative amnesia, depersonalization, dereal-ization, and identity confusion/identity fragmentation. Well-known self-reportquestionnaires that evaluate the severity of dissociation, such as the Dissocia-tive Experiences Scale (DES; Bernstein & Putnam, 1986) and the Dissoci-ation Questionnaire (DIS-Q; Vanderlinden, 1993), predominantly encompasslargely similar, empirically derived factors. As these clusters and factorsinvolve manifestations of dissociation of psychological variables (dissociativeamensia, depersonalization, derealization, identity confusion, identity frag-mentation), we have proposed to name these phenomena psychological dis-sociation (Nijenhuis, Spinhoven, Van Dyck, Van der Hart & Vanderlinden,1996).
Do these symptom clusters encompass all major symptoms of dissociative disorders? Does dissociation indeed only manifest in psychological variables,leaving the body unaffected? In the aforementioned descriptive definitionsand instruments that evaluate dissociation and dissociative disorders, thatwould seem to be the case. This impression is amplified when one studies theDSM-IV criteria for the dissociative disorders. The only diagnostic criteriathat refer to the body can be found under depersonalization disorder, whichstates that the person can feel detached from, and as if one is an outsideobserver of, one’s body, or parts of the body. It is also stated that dissociativedisorders may involve a disruption of the usually integrated function ofperception of the environment and the diagnostic features of depersonaliza-tion disorder include various types of sensory anesthesia. Yet, patients withdissociative disorders report many somatoform symptoms, and many meetthe DSM-IV criteria of somatization disorder or conversion disorder (Pribor,Yutzy, Dean & Wetzel, 1993; Ross, Heber, Norton & Anderson, 1989; Saxeet al., 1994). On the other hand, patients with somatization disorder oftenhave amnesia (Othmer & De Souza, 1985). Although somatoform disordersare not conceptualized as dissociative disorders in the DSM-IV, the strongcorrelation between dissociative and somatoform disorders (see also Darves-Bornoz, 1997) indicates that dissociation and so-called conversion symp-toms, and particular somatization symptoms, may be manifestations of asingle underlying principle.
The major symptoms of hysteria, which involve both mind and body–a cluster of disorders that prominently included the current dissociative disor- ders–are another indication of the existence of somatoform dissociation, aconcept with origins in 19th century French psychiatry. During that timemany authors focused, exclusively or primarily, on the somatoform man-ifestations of hysteria (e.g., Briquet, 1859). As Van der Hart and colleagues(Van der Hart, Van Dijke, Van Son, & Steele, 2000, this issue) have clearlydemonstrated, somatoform dissociation characterized many traumatizedWorld War I soldiers as well. Recent clinical observations also indicate thatdissociation can manifest in somatoform ways (Cardeña, 1994; Kihlstrom,1994; Nemiah, 1991; Van der Hart & Op den Velde, 1995). Furthermore, theInternational Classification of Diseases, Tenth Edition (ICD-10; WorldHealth Organization, 1992) includes somatoform dissociation within disso-ciative disorders of movement and sensation: a category listed as ‘‘conver-sion disorder’’ in the DSM-IV. Confusion exists within both classificatorysystems as well. For example, whereas the ICD-10 includes the diagnosticcategory of dissociative anesthesia, the ICD-10 and the DSM-IV both includesymptoms of anesthesia–among many other symptoms–under somatizationdisorder. Pain symptoms and sexual dysfunctions are not described as con-version symptoms or dissociative symptoms, yet according to clinical ob-servation they can represent definitive dissociative phenomena. For instance,localized pain may be dependent on the reactivation of a traumatic memorythat was previously dissociated and manifests as physical pain in a particularbody part. In fact, traumatic memories primarily include a range of sensori-motor reactions (Nijenhuis, Van Engen, Kusters & Van der Hart, in press; Vander Hart et al., 2000, this issue; Van der Kolk & Fisler, 1995).
In order to avoid confusion, it is important to stress that the labels ‘‘psy- chological dissociation’’ and ‘‘somatoform dissociation’’ should not be takento mean that only psychological dissociation is a mental phenomenon. Bothdescriptors refer to the ways in which dissociative symptoms may manifest,not to their presumed cause. Somatoform dissociation designates dissociativesymptoms that phenomenologically involve the body, and psychological dis-sociative symptoms are those that phenomenologically involve psychologicalvariables. The descriptor ‘‘somatoform’’ indicates that the physical symp-toms resemble, but cannot be explained by, a medical symptom or the directeffects of a substance. In the term ‘‘somatoform dissociation,’’ ‘‘dissoci-ation’’ describes the existence of a disruption of the normal integrative men-tal functions. Thus ‘‘somatoform dissociation’’ denotes phenomena that aremanifestations of a lack of integration of somatoform experiences, reactions,and functions.
This article will review recent empirical studies of somatoform dissoci- ation. These studies investigated the extent to which somatoform dissoci-ation: (1) can be measured, (2) correlates with psychological dissociation,(3) belongs to the major symptoms of dissociative disorders, (4) discrimi- JOURNAL OF TRAUMA & DISSOCIATION nates among various diagnostic categories, (5) depends on culture, (6) re-flects general psychopathology, (7) depends on suggestion, (8) is characteris-tic of dissociative disorders, and can be used in the screening for thesedisorders, (9) is associated with (reported) trauma among psychiatric patientsand patients presenting in medical health care settings, and (10) relates toanimal defense-like reactions. The review of these studies is preceded bybrief descriptions of Janet’s view on hysteria and Myers’ (1940) view on‘‘shell shock,’’ or war-related traumatization.
JANET’S CLASSIFICATION OF DISSOCIATIVE SYMPTOMS
Janet’s clinical observations suggested that hysteria involves psychologi- cal and somatoform functions and reactions (Janet, 1889, 1893, 1901/1977).
In his view, mind and body were inseparable, thus his classification of thesymptoms of hysteria does not follow a mind-body distinction. He main-tained that apart from the permanent symptoms, termed ‘‘mental stigmata,’’that mark all cases of hysteria, there are incidental symptoms, that is, symp-toms that depend on each case. Janet referred to these intermittent and vari-able symptoms as ‘‘mental accidents’’ (Van der Hart & Friedman, 1989).
Janet observed that mental stigmata include functional losses including partial or complete loss of knowledge (amnesia), loss of sensations such asloss of tactile sensations, kinesthesia, smell, taste, hearing, vision, and painsensitivity (analgesia), and loss of motor control (inability to move or speak).
We have referred to mental stigmata as negative symptoms (Nijenhuis & Vander Hart, 1999).
Janet defined mental accidents as incidental symptoms, i.e., symptoms that vary by case and are often more transitory in nature. In our view, mentalaccidents represent positive symptoms because they involve additions, i.e.,mental phenomena that should have been integrated in the personality, butbecause of integrative failure become dissociated material that intrudes intoconsciousness at times. Examples include reexperiencing more or less com-plete traumatic memories and manifestations of dissociative personalities.
According to Janet, the simplest form of mental accidents are ‘‘idées fixes’’ (fixed ideas), that are related to intrusions of some dissociated emo-tion, thought, sensory perception, or movement. This intrusion into or inter-ruption of the personality may also pertain to ‘‘hysterical attacks,’’ to theextent to which they are reactivations of traumatic memories. Janet observedthat some disssociative patients are subject to ‘‘somnambulisms,’’ whichtoday may be recognized as the activities of dissociative identities (APA,1994). (Since these mental structures involve far more than merely a differentsense of self, we feel they are better referred to as dissociative personalities (Nijenhuis, Van der Hart, & Steele, in press).) When patients lose all touchwith reality during dissociative episodes, they experience a ‘‘delirium,’’ i.e., areactive dissociative psychosis (Van der Hart, Witztum, & Friedman, 1993).
Janet (1889, 1893, 1901/1977, 1907) gave many clinical examples show- ing that dissociative mental structures can involve dissociated sensory, motor,and other bodily reactions and functions in addition to dissociated emotionsand knowledge. The symptoms can vary within each dissociative mentalstructure. For example, in one dissociative personality the patient may beinsensitive to pain (analgesic) or touch (tactile anesthesia), but in another,these mental stigmata can be absent, or exchanged for mental accidents, suchas localized pain. Whatever has not been integrated into one dissociativepersonality (not-knowing; not-sensing; not-perceiving) is often prominent inanother: a memory; a thought; a bodily feeling, or a complexity of sensations,motor reactions, and other experiential components that could manifest in‘‘hysterical attacks.’’ Janet’s dissociation theory postulates that both somatoform and psycho- logical components of experience, reactions, and functions can be encodedinto mental systems that can escape integration into the personality (Janet,1889, 1893, 1901/1977, 1911). He used the construct ‘‘personality’’ to denotethe extremely complex, but largely integrated, mental system that encom-passes consciousness, memory, and identity. Janet observed that dissociativemental systems are also characterized by a retracted field of consciousness,that is, a reduced number of psychological phenomena that can be simulta-neously integrated into one and the same mental system.
In Janet’s conceptualization, mental accidents represent reactivations of what has been encoded and stored in dissociative ‘‘systems of ideas andfunctions.’’ Due to recurrent dissociation and imagery, these systems canbecome emancipated. That is, dissociative systems may synthesize and as-similate more sensations, feelings, emotions, thoughts, and behaviors in thecontext of recurrent traumatization or reactivation by trauma-related condi-tioned stimuli. As a result, these systems may become associated with a rangeof experiences, a name, age, and other personality-like characteristics. Today,these emancipated systems are described as more or less complex dissocia-tive personalities whose personality-like features may result from secondaryelaborations (Nijenhuis, Spinhoven, Vanderlinden, Van Dyck, & Van derHart, 1998). These elaborations are probably promoted by hypnotic-likeimagination, restricted fields of consciousness, and needs that are associat-ed with these dissociative mental systems. To a yet unknown extent, sec-ondary shaping of dissociative mental systems by sociocultural influencesmay also be involved (Gleaves, 1996; Janet, 1929; Laria & Lewis-Fernández,in press).
JOURNAL OF TRAUMA & DISSOCIATION THE ‘‘APPARENTLY NORMAL’’ PERSONALITY
AND THE ‘‘EMOTIONAL’’ PERSONALITY
Many cases of dissociative disorder predominantly remain in a condition that has been described as an ‘‘apparently normal’’ personality (Myers, 1940;Nijenhuis & Van der Hart, 1999; Van der Hart, Van der Kolk, & Boon, 1998;Van der Hart et al., 2000, this issue). As ‘‘apparently normal’’ personality, thepatient on the surface appears as more or less mentally normal. However, oncloser scrunity he or she is characterized by a range of negative symptoms(Nijenhuis & Van der Hart, 1999). Examples of these negative symptoms arepartial or complete amnesia and anesthesia. The ‘‘apparently normal’’ per-sonality, which in dissociative identity disorder (DID) can be fragmented intotwo or more personalities, is structurally dissociated from one or more ‘‘emo-tional’’ personalities (Nijenhuis, Van der Hart et al., in press; Van der Hart,2000; Van der Hart et al., 2000, this issue). In our view, dissociative mentalsystems that involve ‘‘emotional’’ personalities–ranging from Janetian idéesfixes to somnambulisms–often encompass traumatic memories, or aspectsthereof, and defensive reactions to major threat (Nijenhuis, Vanderlinden, &Spinhoven, 1998; Nijenhuis, Spinhoven, Vanderlinden et al., 1998). Thus, the‘‘emotional’’ personality–whatever its degree of complexity and emancipa-tion–constitutes a positive symptom. However, as to content, ‘‘emotional’’personalities can contain negative or positive symptoms, or both. Negativesymptoms of ‘‘emotional’’ personalities include analgesia and motor inhibi-tions that are expressions of defensive freezing. Examples of positive symp-toms include particular trauma-related movements and pain. Because disso-ciative barriers are not absolute, ‘‘emotional’’ personalities may influence the‘‘apparently’’ normal personality and, when applicable, vice versa. Alterna-tion between both types of personalities occurs in mental disorders rangingfrom posttraumatic stress disorder to DID (Nijenhuis & Van der Hart, 1999).
Table 1 summarizes the clinically observed dissociative symptoms along two dichotomous types of phenomena. One type of phenomena are mentalstigmata/negative symptoms and mental accidents/positive symptoms, andthe other phenomena are psychological and somatoform manifestations of acommon dissociative process.
THE SOMATOFORM DISSOCIATION QUESTIONNAIRE
The severity of somatoform dissociation can be measured with the Soma- toform Dissociation Questionnaire (SDQ-20, see Appendix), a 20 item self-report instrument with excellent psychometric characteristics (Nijenhuis et al.
1996, 1998a, Nijenhuis, Van Dyck, Spinhoven et al., 1999). The items of the TABLE 1. A Phenomenological Categorization of Dissociative Symptoms fixed ideas: singularintrusive somatoformsymptoms whichinfluence the habitualstate complexes ofsomatoform symptomswhich influence thehabitual state of state, which involvecomplex somatoformalterations state, which involvegrotesque somatoformalterations and enduringfailure to test reality SDQ-20 include negative and positive symptoms, and converge with themajor symptoms of hysteria formulated by Janet a century ago. Examples ofsensory losses are analgesia (‘‘Sometimes my body, or a part of it, is insensi-tive to pain’’), kinesthetic anesthesia (‘‘Sometimes it is as if my body, or apart of it, has disappeared’’), and motor inhibitions (‘‘Sometimes I am para-lysed for a while’’; ‘‘Sometimes I cannot speak, or only whisper’’). Anesthe-sia also pertains to visual (‘‘Sometimes I cannot see for a while’’), andauditory perception (‘‘Sometimes I hear sounds from nearby as if they werecoming from far away’’). Positive symptoms include ‘‘Sometimes I have painwhile urinating,’’ and ‘‘Sometimes I feel pain in my genitals’’ (at times otherthan sexual intercourse).
In seven studies performed to date, age and gender did not have a signifi- cant effect on somatoform dissociation as measured by the SDQ-20. Howev-er, in a sample of psychiatric outpatients (N = 153), women had slightlyhigher scores than men (Nijenhuis, Van der Hart, & Kruger, submitted), and JOURNAL OF TRAUMA & DISSOCIATION in Turkey, a weak but statistically significant correlation with age was found(Sar, Kundakci, Kiziltan, Bakim, & Bozkurt, 2000, this issue).
SOMATOFORM DISSOCIATION
AND PSYCHOLOGICAL DISSOCIATION
In all but one study performed to date, somatoform dissociation was strongly associated with psychological dissociation as measured by the DESand DIS-Q, ranging from r = 0.62 (Nijenhuis et al., submitted) to r = 0.85(Nijenhuis, Van Dyck, Spinhoven et al., 1999). Waller et al. (2000, this issue)found a lower correlation among psychiatric outpatients in the United King-dom (r = 0.51). These results suggest that while somatoform and psychologi-cal dissociation are manifestations of a common process, they are not com-pletely overlapping. Somatoform and psychological dissociation during orimmediately after the occurrence of a traumatic event, i.e., peritraumaticdissociation, were also significantly correlated (Nijenhuis, Van Engen et al.,in press).
SOMATOFORM DISSOCIATION IN VARIOUS DIAGNOSTIC
GROUPS IN THE NETHERLANDS AND BELGIUM
A range of contemporary studies have revealed that somatoform dissoci- ation is a unique construct and a major feature of dissociative disorders(Nijenhuis et al., 1996, 1998a; Nijenhuis, Van Dyck, Spinhoven et al., 1999).
Patients with DSM-IV dissociative disorders had significantly higherSDQ-20 scores than psychiatric outpatients with other DSM-IV diagnoses,and patients with dissociative identity disorder (DID) had higher scores thanpatients with dissociative disorder, not otherwise specified (DDNOS) or de-personalization disorder (Nijenhuis et al., 1996, 1998a).
In Dutch samples, the SDQ-20 discriminated among various diagnostic categories (Nijenhuis, Van Dyck, Spinhoven et al., 1999). Compared to pa-tients with DDNOS or depersonalization disorder, patients with DID hadsignificantly higher scores. Patients with DDNOS had statistically signifi-cantly higher scores than patients with somatoform disorders or eating disor-ders, and the latter two diagnostic categories were associated with signifi-cantly higher scores than patients who had anxiety disorder, depression,adjustment disorders and bipolar mood disorders (see Table 2). In particular,bipolar mood disorder was associated with extremely low somatoform dis-sociation (see also Nijenhuis, Spinhoven, Van Dyck, Van der Hart, De Graafet al., 1997).
TABLE 2. Somatoform Dissociation as Measured by the SDQ-20 in VariousDiagnostic Groups conversion disorder (n = 32), paindisorder (n = 7), conversion andpain disorder (n = 5), somatizationdisorder (n = 4) In contrast with the SDQ-20, the DES did not discriminate between bipo- lar mood disorder and somatoform disorders. In a sample that primarilyincluded cases of DSM-IV conversion and pain disorder and no cases ofhypochondriases, the results suggest that patients with these particular soma-toform disorders have significant somatoform dissociation, but less psycho-logical dissociation (Nijenhuis, Van Dyck, Spinhoven et al., 1999).
IS SOMATOFORM DISSOCIATION
A CULTURALLY-DEPENDENT PHENOMENON?
Our consistent finding that somatoform dissociation is extremely charac- teristic of DSM-IV dissociative disorders, in particular DID, has been corrob- JOURNAL OF TRAUMA & DISSOCIATION orated by findings in some other countries and cultures (see Table 2). In theUSA, Chapperon (personal communication, September 1996) found highsomatoform dissociation among DID patients, and Dell (1997a) reported thatDID patients had significantly higher scores than patients with DDNOS,eating disorders, or pain disorder. Studying various diagnostic categories inTurkey, Sar and colleagues (Sar, Kundakci, Kiziltan, Bahadir, and Aydiner,1998; Sar et al., 2000, this issue) obtained results that are remarkably similarto ours: somatoform dissociation was extreme in DSM-IV dissociative disor-ders, quite modest in anxiety disorders, major depression, and schizophrenia,and low in bipolar mood disorder. Also consistent with our data, both Dell(1997a) and Sar et al. (1998, 2000, this issue) found strong intercorrelationsof SDQ-20 and DES scores. Van Duyl’s (personal communication, March2000) data on somatoform dissociation among dissociative disorder patientsin Uganda converge with our Dutch/Flemish results as well. Conjointly, theseinternational findings suggest that somatoform dissociation is highly charac-teristic of dissociative disorders, that somatoform and psychological dissoci-ation are closely related constructs, and that the severity of somatoformdissociation among dissociative disorder patients from these cultures is large-ly comparable. Moreover, somatoform dissociative symptoms and disordersalso manifested among tortured Bhutanese refugees, in particular those withPTSD (Van Ommeren et al., in press).
IS SOMATOFORM DISSOCIATION A UNIQUE CONSTRUCT?
Considering the moderate to high correlation between general psycho- pathology and psychological dissociation (Nash, Hulsey, Sexton, Harralson, &Lambert, 1993; Norton, Ross, & Novotny, 1990), some have expressed con-cern that dissociation scales may assess the former concept rather than thelatter (Tillman, Nash, & Lerner, 1994). These authors could be correct, butthis correlation could also reflect the broad comorbidity that characterizescomplex dissociative disorders.
To study whether somatoform dissociation could possibly reflect general psychopathology, Nijenhuis, Van Dyck, Spinhoven et al. (1999) statisticallyadjusted the somatoform dissociation scores of different diagnostic catego-ries for the influence of general psychopathology as assessed by the SymptomChecklist (SCL-90-R; Derogatis, 1977). The adjusted scores discriminatedamong DID, DDNOS, somatoform disorders, bipolar mood disorder, andeating disorders, and mixed psychiatric disorders (Nijenhuis, Van Dyck,Spinhoven et al., 1999). Therefore, it was concluded that somatoform dis-sociation is a unique construct, unrelated to general levels of psychopathology.
DOES SOMATOFORM DISSOCIATION
RESULT FROM SUGGESTION?
Another concern is whether suggestion affects somatoform dissociation scores. For example, Merskey (1992, 1997) maintained that dissociative disor-der patients are extremely suggestible, and therefore vulnerable to indoctrina-tion by therapists who mistake the symptoms of bipolar mood disorder for‘‘dissociative’’ symptoms.
In a single case study with positron emission tomography (PET) function- al imaging, hypnotic paralysis activated brain areas similar to those in pa-tients with conversion disorder, which could indicate that hypnosis and soma-toform dissociation share common neurophysiological mechanisms (Halligan,Athwal, Oakley, & Frackowiak, 2000). This case study obviously requiresreplication among a group of patients with somatoform dissociative disor-ders, and the observed correlation does not document a causal relationship.
There are noteworthy reasons to believe that suggestion and indoctrination do not explain somatoform dissociation. Patients who completed the SDQ-20in the assessment phase, and prior to the SCID-D interview, had higher scoresthan dissociative patients who completed the instrument in the course of theirtherapy (Nijenhuis, Van Dyck, Van der Hart, & Spinhoven, 1998; Nijenhuis,Van Dyck, Spinhoven et al., 1999). Moreover, prior to our research, thesymptoms described by SDQ-20 were not known as major symptoms ofdissociative disorders among diagnosticians and therapist, let alone patients.
It was also found that the dissociative patients who were in treatment with thepresent author did not exceed the SDQ-20 scores of dissociative patients whowere treated by other therapists. Given this author’s theoretical orientationand expectations, he was the most likely person to suggest somatoform disso-ciative symptoms (Nijenhuis, Spinhoven, Vanderlinden et al., 1998). Hence,the available empirical data run contrary to the hypothesis that somatoformdissociation results from suggestion.
SOMATOFORM DISSOCIATION IN THE SCREENING
FOR DSM-IV DISSOCIATIVE DISORDERS
The data discussed so far reveal that somatoform dissociation is very characteristic of patients with DDNOS and DID. The question remainswhether somatoform dissociation is as characteristic of these disorders aspsychological dissociation. This issue required examination of the relativeability of somatoform and psychological dissociation screening instrumentsto discern between those cases with DSM-IV dissociative disorders, andthose without.
JOURNAL OF TRAUMA & DISSOCIATION The SDQ-5, comprised of 5 items from the SDQ-20, was developed as a screening instrument for DSM-IV dissociative disorders (Nijenhuis, Spinho-ven, Van Dyck, Van der Hart, & Vanderlinden, 1997; Nijenhuis et al., 1998a).
The sensitivity (the proportion of true positives selected by the test) of theSDQ-5 among SCID-D assessed patients with dissociative disorders in vari-ous Dutch/Flemish samples (N = 50, N = 33, N = 31, respectively) rangedfrom 82% to 94%. The specificity (the proportion of the comparison patientsthat is correctly identified by the test) of the SDQ-5 ranged from 93% to 98%(N = 50, N = 42, N = 45, respectively). The positive predictive value (theproportion of cases with scores above the chosen cut-off value of the test thatare true positives) among these samples ranged from 90% to 98%, and thenegative predictive value (the proportion of cases with scores below thiscut-off value that are true negatives) from 87% to 96%. The correspondingvalues of the SDQ-20 were slightly lower (Nijenhuis et al., 1997).
High sensitivity and specificity of a test do not implicate a high predictive value when the prevalence of the disorder in the population of concern is low(Rey, Morris-Yates, & Stanislaw, 1992). The prevalence of dissociative disor-ders among psychiatric patients has been estimated at approximately 8%-15%(Friedl & Draijer, 2000; Horen, Leichner, & Lawson, 1995; Sar et al., 1999;Saxe et al., 1993). Corrected for a prevalence rate of 10%, the positivepredictive values among the indicated samples ranged from 57% to 84%, andthe negative predictive values from 98% to 99%. Averaged over three sam-ples, the positive predictive value of the SDQ-5 was 66%. Hence, it can bepredicted that among Dutch/Flemish samples, two of three patients withscores at or above the cut-off will have a DSM-IV dissociative disorder.
Among Dutch dissociative disorder patients and psychiatric comparison patients, Boon and Draijer (1993) found that the sensitivity of the DES was93%, the specificity 86%, the corrected positive predictive value 42%, andthe corrected negative predicted value 99%. It thus seems that somatoformdissociation is at least as characteristic of complex dissociative disorders as ispsychological dissociation in Dutch samples.
IS SOMATOFORM DISSOCIATION CORRELATED
WITH REPORTED TRAUMA?
In our study comparing dissociative disorder patients (N = 45) with con- trol patients (N = 43) (Nijenhuis, Spinhoven, Van Dyck, Van der Hart, &Vanderlinden, 1998b), the dissociative disorder patients reported severe andmultifaceted traumatization on the Traumatic Experiences Checklist (TEC;Nijenhuis, Van der Hart, & Vanderlinden; see Nijenhuis, 1999). Among vari-ous types of trauma, physical abuse, with an independent contribution ofsexual trauma, best predicted somatoform dissociation. Sexual trauma best predicted psychological dissociation. According to the reports of the disso-ciative disorder patients, this abuse usually occurred in an emotionally ne-glectful and abusive social context. Both somatoform and psychologicaldissociation were best predicted by early onset of reported intense, chronicand multiple traumatization.
Reanalysing the data of this study, it was found that the total TEC score explained 48% of the variance of somatoform dissociation, a value thatexceeded the variance explained by reported physical and sexual abuse (Nijen-huis, 1999). This additional finding suggests that somatoform dissociation isstrongly associated with reported multiple types of trauma: a finding thatconverges with the results of research in the incidence of verified multipleand chronic traumatization in DID patients (Coons, 1994; Hornstein & Put-nam, 1992; Kluft, 1995; Lewis, Yeager, Swica, Pincus, & Lewis, 1997).
Studying psychiatric outpatients, both Waller and his colleagues (2000, this issue) and Nijenhuis et al. (submitted) also found that among varioustypes of trauma, somatoform dissociation was best predicted statistically byphysical abuse and threat to life by another person. Preliminary North Ameri-can findings (Dell, 1997b) have indicated moderate to strong statisticallysignificant correlations among somatoform dissociation and reported sexualabuse (r = .51), sexual harassment (r = .49), physical abuse (r = .49), andlower correlations with reported emotional neglect (r = .25) and emotionalabuse (r = .31). Reported early onset of traumatization was somewhat morestrongly associated with somatoform dissociation than was trauma reportedin later developmental periods, and among all variables tested the total trau-ma score was associated with somatoform dissociation most strongly (r =.63). These various results are highly consistent with our findings. It can beconcluded that somatoform dissociation is particularly associated with physi-cal abuse and sexual trauma, thus with threat to the integrity of the body.
Consistent with this conclusion, Van Ommeren et al. (in press) found thattortured Bhutanese refugees (N = 526), compared with nontortured Bhuta-nese refugees, had significantly more lifetime ICD-10 (WHO, 1992) persis-tent somatoform pain disorder (56.2% vs. 28.8%), dissociative motor disor-der (11.2% vs. 1.3%), and dissociative anesthesia and sensory loss (14.4% vs.
2.8%).
A link between somatoform dissociation and reported trauma is also sug- gested by studies that have found associations between somatization symp-toms, somatoform disorders and reported trauma. For example, undifferen-tiated somatoform disorder belonged to the three DSM-IV Axis I diagnosesthat marked Gulf War veterans referred for medical and psychiatric syn-dromes (Labbate, Cardeña, Dimitreva, Roy, & Engel, 1998). More specifical-ly, reports of traumatic events were correlated with both PTSD and somato-form diagnoses, and veterans who handled dead bodies had a three-fold risk JOURNAL OF TRAUMA & DISSOCIATION of receiving a somatoform diagnosis. In addition, a range of studies foundassociations among (reported) trauma, psychological dissociation, and soma-tization symptoms or somatoform disorders (e.g., Atlas, Wolfson, & Lips-chitz, 1995; Darves-Bornoz, 1997; Van der Kolk et al., 1996).
SOMATOFORM DISSOCIATION
AND ANIMAL DEFENSIVE REACTIONS
Patients with DID or related types of DDNOS remain in alternating disso- ciative personalities (in varying degrees of complexity) that are relativelydiscrete, discontinuous, and resistant to integration. In our view, basicallythey represent ‘‘apparently normal’’ and ‘‘emotional’’ personalities (Nijen-huis & Van der Hart, 1999), and are associated with particular somatoformdissociative symptoms. Exploring the roots of these dissociative mental sys-tems and symptoms, Nijenhuis, Vanderlinden, and Spinhoven (1998) drew aparallel between animal defensive and recuperative states evoked in the faceof variable predatory imminence and injury, and characteristic somatoformdissociative responses of patients with dissociative disorders who report trau-ma. Their review of empirical data of research with animals and humans, aswell as clinical observations, suggested that there are similarities betweendisturbances of normal eating-patterns and other normal behavioral patternsin the face of diffuse threat. Freezing and stilling occur when serious threatmaterializes; analgesia and anesthesia when strike is about to occur; andacute pain when threat has subsided and actions that promote recuperationfollow. According to our structural dissociation model (Nijenhuis, Van derHart, & Steele, in press), ‘‘emotional’’ personalities would involve animaldefense-like systems, and ‘‘apparently normal’’ personalities would exhibit arange of behavioral and mental reactions to avoid or escape from traumaticmemories and the associated ‘‘emotional’’ personality. In our view, the men-tal avoidance and escape reactions, among others, find expression in negativepsychological and somatoform dissociative symptoms, such as amnesia andemotional as well as sensory anesthesia.
Consistent with this model, several studies have suggested that threat to life, whether due to natural or human causes, may induce analgesia andnumbness (Cardeña et al., 1998; Cardeña & Spiegel, 1993; Pitman, Van derKolk, Orr, & Greenberg, 1990; Van der Kolk, Greenberg, Orr, & Pitman,1989). Nijenhuis, Spinhoven and Vanderlinden et al. (1998) performed thefirst test of the hypothesized similarity between animal defensive reactionsand certain somatoform dissociative symptoms of dissociative disorder pa-tients who reported trauma. Twelve somatoform symptom clusters consistingof clinically observed somatoform dissociative phenomena were constructed.
All clusters discriminated between patients with dissociative disorders and patients with other psychiatric diagnoses. Those expressive of the hypothe-sized similarity–freezing, anesthesia-analgesia, and disturbed eating–belongedto the five most characteristic symptoms of dissociative disorder patients.
Anesthesia-analgesia, urogenital pain and freezing symptom clusters inde-pendently contributed to predicted caseness of dissociative disorder. Using anindependent sample, it appeared that anesthesia-analgesia best predictedcaseness after controlling for symptom severity. The indicated symptom clus-ters correctly classified 94% of cases that constituted the original sample, and96% of the independent second sample. These results were largely consistentwith the hypothesized similarity.
The anesthesia symptoms characterize ‘‘emotional’’ personalities, but may also be part and parcel of ‘‘apparently normal’’ personalities. In our view,‘‘apparently normal’’ personalities are phobic of traumatic memories andphobic of the associated ‘‘emotional’’ personalities (Nijenhuis & Van derHart, 1999; Nijenhuis, Van der Hart et al., in press). This phobia manifests intwo major negative dissociative symptoms: amnesia and sensory, as well asemotional anesthesia. Recent data from psychobiological experimental re-search with both types of dissociative personalities support this interpretation(Nijenhuis, Quak et al., 1999; Van Honk, Nijenhuis, Hermans, Jongen, & Vander Hart, 1999).
IS SOMATOFORM DISSOCIATION ALSO ASSOCIATED
WITH DISSOCIATIVE DISORDER AND TRAUMA
IN A NONPSYCHIATRIC POPULATION?
In order to test the generalizability of the powerful associations between somatoform dissociation, dissociative disorder, and reported trauma amongpsychiatric patients, we investigated whether these relationships would alsohold among a nonpsychiatric population (Nijenhuis, Van Dyck, Ter Kuile etal., 1999). According to the literature, chronic pelvic pain (CPP) is one of thesomatic symptoms that, at least among a subgroup of gynecology patients,relates to reported trauma (e.g., Walling et al., 1994; Walker et al., 1995) anddissociation (Walker et al., 1992). In this population (N = 52), psychologicaldissociation and somatoform dissociation were significantly associated with(features of) DSM-IV dissociative disorders, as measured by the SCID-D.
Anxiety, depression, and psychological dissociation best predicted the SCID-D total score, whereas amnesia was best predicted by somatoform dissoci-ation. Identity confusion was best predicted by anxiety/depression and soma-toform dissociation. These findings ran partly contrary to our hypothesis thatsomatoform dissociation among CPP patients would be more predictive ofdissociative disorder than psychological dissociation.
In this study, the sensitivity of somatoform and psychological dissociation JOURNAL OF TRAUMA & DISSOCIATION screening instruments for dissociative disorders was 100%. The specificitywas 90.2% (SDQ-5) and 94.1% (DES) respectively. Somatoform dissociationwas strongly associated with, and best predicted, reported trauma. Physicalabuse, life threat posed by a person, sexual trauma, and intense pain bestpredicted somatoform dissociation among the various types of trauma. Physi-cal abuse/life threat posed by a person remained the best predictor of somato-form dissociation after statistically controlling for the influence of anxiety,depression, and intense pain (Nijenhuis, Van Dyck, Ter Kuile et al., 1999).
This study demonstrated a strong association between somatoform dis- sociation and reported trauma in a nonpsychiatric population, as well as aconsiderable association between somatoform dissociation and features ofdissociative disorders. The results are consistent with our findings amongpsychiatric patients, and, therefore, strengthen our thesis that somatoformdissociation, features of dissociative disorders, and reported trauma arestrongly intercorrelated phenomena.
DISCUSSION
The items of the SDQ comprise many of the symptoms that mark hysteria as described by Janet (1893, 1907). The reviewed empirical data show thatthe 19th century symptoms of hysteria are very characteristic of the 20thcentury dissociative disorders. They confirm that these symptoms involve acombination of mental stigmata (the negative symptoms of anesthesia, anal-gesia, and motor inhibitions) and mental accidents (the positive symptoms oflocalized pain, and alternation of taste and smell preferences/aversions). Al-though I subscribe to the Janetian position that body and mind are insepara-ble, I insist that making a phenomenological distinction among psychologicaland somatoform manifestations of dissociation can be clarifying, in that ithighlights the largely forgotten or ignored clinical–and now empirically sub-stantiated–observation that dissociation also pertains to the body.
No indications were found suggesting that these symptoms were man- ifestations of general psychopathology, or were a consequence of suggestion.
Obviously, this is far from saying that dissociative disorder patients areimmune to suggestion, or denying that there are factituous dissociative disor-der cases (Draijer & Boon, 1999). However, it seems warranted to state thatsuggestion does not explain the findings of our studies on somatoform dis-sociation.
Somatoform dissociation belongs to the major symptoms of DSM-IV dissociative disorders, but it also characterizes many cases of DSM-IV soma-toform disorders, as well as a subgroup of patients with eating disorders. Likedissociative disorders, somatization disorder (Briquet’s syndrome) has rootsin hysteria: Briquet’s pioneering research revealed that many patients with hysteria had amnesia, in addition to many somatoform symptoms. Contem-porary research also shows that psychological dissociation and somatizationare related phenomena. For example, Saxe et al. (1994) found that abouttwo-thirds of the patients with dissociative disorders met the DSM-IV criteriaof somatization disorder. Yet somatization probably is neither a distinct clini-cal entity, nor the result of a single pathological process (Kellner, 1995). Itseems likely that somatoform dissociation pertains to a subgroup of somato-form symptoms that remain medically unexplained, or difficult to explain.
The findings of our studies are more consistent with the ICD-10 (WHO, 1992), that includes dissociative disorders of movement and sensation, thanto the DSM-IV, that restricts dissociation to psychological manifestations andregards somatoform manifestations of dissociation as ‘‘conversion symp-toms.’’ However, the SDQ-5 in the Netherlands, and the SDQ-20 in Turkey,were at least as effective as the DES in the screening for DSM-IV dissocia-tive disorders, and our finding that psychological and somatoform dissoci-ation are strongly associated suggests that both phenomena are manifestationsof a common (pathological) process. Moreover, somatoform dissociation hasbeen demonstrated to be characteristic of DSM-IV conversion disorder (Kuyk,Spinhoven, Van Emde Boas, & Van Dyck, 1999; for a review, see Bowman &Kuyk, in press), and somatoform dissociation, rather than psychological dis-sociation, was characteristic of patients with pseudo-epileptic seizures (Kuyket al., 1999). Psychological dissociation was also very common among pa-tients with conversion disorders (Spitzer, Spelsberg, Grabe, Mundt, & Frei-berger, 1999).
In conclusion, relabeling conversion (a concept that has links to controver- sial Freudian theory) as somatoform dissociation, and categorizing the DSM-IV conversion disorders as dissociative disorders is indicated. The sameapplies to somatization disorder when it is predominantly characterized bysomatoform dissociation. Such findings would promote a reinstitution of the19th century category of hysteria under the general label of dissociativedisorders, and would include the current dissociative disorders, DSM-IVconversion disorder/ICD-10 dissociative disorders of movement and sensa-tion, and somatization disorder. On the other hand, analysis of somatoformdissociation in DSM-IV somatization disorder may also reveal the existenceof various subgroups. It could be that a subgroup of patients with somatiza-tion disorder has severe somatoform dissociation, whereas another subgroupobtains low or modest somatoform dissociation scores. It also seems doubtfulthat, for example, conversion disorder and hypochondriasis relate to similarpathology. Hence, further study of somatoform dissociation in the variousDSM-IV somatoform disorders is needed.
The hypothesized dissociative personality-dependent nature of somato- form dissociation cannot be studied with the regular use of the SDQ-20 and JOURNAL OF TRAUMA & DISSOCIATION SDQ-5, but must be analysed using other methods. These include repeatedadministration of these instruments to DID patients while they remain in‘‘apparently normal’’ and ‘‘emotional’’ personalities, and to controls whilethey maintain simulated ‘‘apparently normal’’ and ‘‘emotional’’ personali-ties. More important approaches, however, include the study of somatoformdissociative symptoms and concurrent psychophysiological and endocrino-logical reactions while DID patients and controls remain in these respectivelyauthentic and enacted personalities as they are experimentally exposed tomemories of trauma (Nijenhuis, Quak et al., 1999) or masked threat cues(Van Honk et al., 1999).
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JOURNAL OF TRAUMA & DISSOCIATION SDQ-20
This questionnaire asks about different physical symptoms or body experiences, which you
may have had either briefly or for a longer time.
Please indicate to what extent these experiences apply to you in the past year.
For each statement, please circle the number in the first column that best applies to YOU.
The possibilities are: 1 = this applies to me NOT AT ALL 2 = this applies to me A LITTLE 3 = this applies to me MODERATELY 4 = this applies to me QUITE A BIT5 = this applies to me EXTREMELY If a symptom or experience applies to you, please indicate whether a physician has
connected it with a physical disease.
Indicate this by circling the word YES or NO in the column ‘‘Is the physical cause known?’’
If you wrote YES, please write the physical cause (if you know it) on the line.
If you have circled a 1 in the first column (i.e., This applies to me NOT AT ALL), you do NOThave to respond to the question about whether the physical cause is known.
On the other hand, if you circle 2, 3, 4, or 5, you MUST circle NO or YES in the ‘‘Is thephysical cause known?’’ column.
Please do not skip any of the 20 questions.
Thank you for your cooperation.
1 = this applies to me NOT AT ALL2 = this applies to me A LITTLE 3 = this applies to me MODERATELY4 = this applies to me QUITE A BIT5 = this applies to me EXTREMELY like (women: at timesOTHER THAN pregnancyor monthly periods) differently than usual (forexample, as if looking througha tunnel, or seeing merely apart of an object) or WORSE than I usually do(even though I do not havea cold) JOURNAL OF TRAUMA & DISSOCIATION Before continuing, will you please check whether you have responded to all 20
statements?
You are asked to fill in and place an X beside what applies to you.
single married living together divorced widower/widow

Source: http://www.enijenhuis.nl/articles/nijenhuis_somatoformdiss.pdf