Childhood Trauma and Dissociation in Schizophrenia

Original Paper Psychopathology 2010;43:33–40 DOI: 10.1159/000255961

Received: August 12, 2008 Accepted after revision: April 23, 2009 Published online: November 6, 2009

Childhood Trauma and Dissociation in Schizophrenia Vedat Sar a Okan Taycan b Nurullah Bolat c Mine Özmen b Alaattin Duran b Erdinç Öztürk a Hayriye Ertem-Vehid d a

Clinical Psychotherapy Unit and Dissociative Disorders Program, Department of Psychiatry, Istanbul Faculty of Medicine, Departments of b Psychiatry and c Child and Adolescent Psychiatry, Cerrahpasa Faculty of Medicine, and d Department of Family Health, Institute of Pediatrics, Istanbul University, Istanbul, Turkey

Key Words Schizophrenia ⴢ Dissociation ⴢ Childhood trauma ⴢ Comorbidity ⴢ Psychosis

Abstract Background: This study is concerned with relationships between childhood trauma history, dissociative experiences, and the clinical phenomenology of chronic schizophrenia. Sampling and Methods: Seventy patients with a schizophrenic disorder were evaluated using the Structured Clinical Interview for DSM-IV, Dissociative Experiences Scale, Dissociative Disorders Interview Schedule, Positive and Negative Symptoms Scales, and Childhood Trauma Questionnaire. Results: Childhood trauma scores were correlated with dissociation scale scores and dissociative symptom clusters, but not with core symptoms of the schizophrenic disorder. Cluster analysis identified a subgroup of patients with high dissociation and childhood trauma history. The dissociative subgroup was characterized by higher numbers of general psychiatric comorbidities, secondary features of dissociative identity disorder, Schneiderian symptoms, somatic complaints, and extrasensory perceptions. A significant majority of the dissociative subgroup fit the diagnostic criteria of DSM-IV borderline personality disorder concurrently. Among childhood trauma types, only physical abuse and physical neglect predicted dissociation. Conclusions: A trauma-related dissociative subtype of schizophrenia is sup-

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ported. Childhood trauma is related to concurrent dissociation among patients with schizophrenic disorder. A duality model based on the interaction of 2 qualitatively distinct psychopathologies and a dimensional approach are proposed as possible explanations for the complex relationship between these 2 psychopathologies and childhood trauma. Copyright © 2009 S. Karger AG, Basel

Introduction

Dissociative disorders are increasingly considered as a chronic complex post-traumatic psychopathology closely related to childhood abuse and/or neglect [1]. Subjects with dissociative disorders frequently report childhood traumas, both in clinical settings [2] and in the general population [3]. Alongside clinical series [4, 5], the relationship between childhood trauma and dissociation has been verified both in prospectively designed studies [6] and using retrospective investigation of highly reliable forensic documents [7]. Recent studies document that patients with schizophrenia [8–11] or psychosis [12–14] also report childhood traumas more frequently than controls. Ten out of eleven recent general population studies have found, even after controlling for other factors (including family history of psychosis), that child maltreatment is significantly related to psychosis [15]. Although considVedat Sar, MD Istanbul Tip Fakultesi Psikiyatri Klinigi TR–34390 Capa Istanbul (Turkey) Tel. +90 212 260 1422, Fax +90 212 261 7004, E-Mail [email protected]

eration of psychological trauma as a direct cause of a pervasive mental illness like schizophrenia is controversial [16], a traumagenic neurodevelopmental model has been proposed to explain a potential relationship [17]. Patients with a schizophrenic disorder may come with concurrent psychiatric conditions, such as major depression, obsessive-compulsive disorder, or substance use disorder [18]. Although there are contradictory findings [19], dissociative symptoms [8, 9, 20, 21] and disorders [10] have also been reported in patients with schizophrenia. Based on clinical phenomenology and childhood trauma history, Ross proposed a dissociative subtype of schizophrenia [22]. In accordance with claims for a direct relationship between schizophrenia and dissociation [23], he also proposed that non-dissociative schizophrenia, the dissociative subtype of schizophrenia, schizodissociative disorder, and dissociative identity disorder (DID) constitute a spectrum. There is convincing evidence that childhood trauma history has at least an impact on the clinical phenomenology of schizophrenia. For instance, in 1 study, severity and frequency of childhood maltreatment were both positively correlated with hallucinations and delusions [24]. Another study demonstrated that child abuse was related to hallucinations (auditory and tactile ones in particular), but not to delusions, thought disorder, or negative symptoms, which are known to be the more robust symptoms of schizophrenia [25]. Patients with schizophrenia not only report childhood trauma frequently, but also have trauma-related symptoms. Schizophrenic patients with a childhood sexual abuse history had higher levels of dissociation, intrusive experiences, and state and trait anxiety than the non-abused schizophrenia group [26]. In a study covering adult traumas as well, two thirds of the patients reported clinically significant trauma symptoms that included (at least) intrusive experiences, defensive avoidance, or dissociation. Delusions were correlated with intrusive experiences, dissociation, and number of significantly elevated trauma scales, whereas hallucinations were correlated with irritability and total number of significantly elevated trauma scales [27]. Greater levels of depression and disturbance of volition were significantly correlated with greater levels of anxious arousal, intrusive experiences, defensive avoidance, dissociation, and the total number of significantly elevated trauma scales. In another study, schizophrenia itself seemed to be associated, independently of trauma and pathological posttraumatic conditions, with a broad range of dissociative symptoms [28]. Pronounced post-traumatic symptoms in schizophrenia were associated with severe additional 34

Psychopathology 2010;43:33–40

psychopathological distress, whereas the increase in dissociation in this group of patients was considered as secondary to the increase in symptom load. In a third study, trauma and dissociation were associated with severer symptoms of schizophrenia [29]. In particular, high dissociation was associated with an increase in symptom load, whereas traumatic events fitting PTSD criterion A of DSM-IV and post-traumatic stress disorder (PTSD) had little or no such effect. Based on this accumulating evidence, the present study was concerned with possible relationships between childhood trauma, dissociative experiences, and the clinical phenomenology of chronic schizophrenia. While inquiring into the characteristics of these associations, the study also tried to determine if there was a trauma-related dissociative subgroup among patients with schizophrenic disorder. Beside correlational analyses between various scale scores, schizophrenic patients with high and low dissociation levels were compared on various clinical measures, including general psychiatric comorbidity and childhood trauma reports. As an examination of the true subgroups derived from a combination of various measures, patients were also classified by an independent cluster analysis directly.

Method Participants All patients with a DSM-IV schizophrenic disorder [30] who were admitted consecutively to the Psychiatric Department of the Istanbul University Cerrahpasa Medical Faculty Hospital during the 2-month study period (December 2005 to January 2006) were considered for participation. The diagnosis was confirmed by the Structured Clinical Interview for DSM-IV (SCID-II) [31]. Approval for the study was obtained from the Ethical Committee of the Cerrahpasa Faculty of Medicine. Patients who agreed to participate in the study provided written informed consent after the study procedures had been fully explained. Reasons for exclusion were: severe cognitive impairment (n = 2), psychosis too severe to cooperate (n = 4), and having received electroconvulsive treatment during the 3-month period prior to the study interview (n = 2) . Among 79 patients who were eligible for the study, 8 patients refused to participate and 1 patient was not able to attend due to illiteracy. Seventy patients comprised the final study group. All patients were receiving neuroleptic drug treatment as prescribed by their attending psychiatrists. Inpatients (n = 21) attended the study interview after a stabilization period for an average duration of 14.9 days (SD = 6.5, range = 3–30). Instruments Structured Clinical Interview for DSM-IV. The SCID is a semistructured interview developed by First et al. [31]. This widely used interview serves as a diagnostic instrument for DSM-IV axis

Sar /Taycan /Bolat /Özmen /Duran / Öztürk /Ertem-Vehid

I psychiatric disorders, except for dissociative disorders. In order to document the whole comorbidity spectrum on a phenomenological basis, all sections of the interview were conducted in the present study, i.e., skipping parts of the interview due to the presence of a supraordinate diagnostic category were not carried out. Scales for the Assessment of Negative (SANS) and Positive (SAPS) Symptoms. Developed by Andreasen [32], the SAPS has 30 items, whereas the SANS has 20. Each item is scored on a 6-point Likert-type scale by an interviewer. The SAPS has an interrater reliability of 0.84, whereas the SANS has an interrater reliability of 0.60. Turkish versions of the scales have good reliability and validity as well [33, 34]. Dissociative Experiences Scale (DES). The DES is a 28-item self-report instrument developed by Bernstein and Putnam [35]. It is not a diagnostic tool but serves as a screening device for chronic dissociative disorders with possible scores ranging from 0 to 100. The Turkish version of the scale has good reliability and validity [36], with a cut-off score of 30 being useful for screening dissociative disorders [37]. Dissociative Disorders Interview Schedule (DDIS). The DDIS is a structured clinical interview consisting of 131 items. It was designed by Ross et al. [38] to diagnose somatization, major depression, borderline personality disorder, and 5 classes of dissociative disorders according to DSM-IV. The schedule also inquires about childhood abuse and neglect and a variety of features associated with dissociative disorders including 11 Schneiderian symptoms, 16 secondary features of DID, and 16 extrasensory experiences. The validity and reliability of the Turkish version has been reported elsewhere [37]. Childhood Trauma Questionnaire (CTQ). The CTQ is a 28item self-report instrument developed by Bernstein et al. [39] that evaluates childhood emotional, physical, and sexual abuse and childhood physical and emotional neglect. Possible scores for each type of childhood trauma range from 5 to 25. The sum of the scores derived from each trauma type provides the total score ranging from 25 to 125. Cronbach’s ␣ for the factors related to each trauma type ranges from 0.79 to 0.94, indicating high internal consistency [39]. The scale also demonstrated good test-retest reliability over a 2- to 6-month interval (intraclass correlation = 0.88). Statistical Analysis Two-group comparisons on continuous variables were conducted using the Student’s t test. The relationships of the CTQ and DES with other variables were evaluated with the Pearson correlation test. Predictive power of various types of childhood trauma on DES scores were evaluated with stepwise linear regression analysis. In order to clarify a potential heterogeneity in the study group, we preferred a k-means cluster analysis which classifies subjects directly without pursuing a difference between variables as either dependent or independent [40]. The k-means algorithm assigns each point to the cluster whose center (also called centroid) is nearest. The center is the average of all the points in the cluster – that is, its coordinates are the arithmetic mean for each dimension separately over all the points in the cluster. The purpose of this method is to demonstrate the presence of patient subgroups with homogenous variables within groups and heterogeneity between groups, where the number of subgroups is to be decided by the investigator but not the method itself. We preferred

Trauma and Dissociation in Schizophrenia

Table 1. Pearson correlations between DES, CTQ, and selected clinical features (n = 70) Clinical characteristics

DES total score CTQ total score Secondary symptoms of DID Number of borderline personality disorder criteria (SCID-II) Extrasensory perceptions Somatic complaints Schneiderian symptoms SCID diagnoses (lifetime) SCID diagnoses (current) SANS SAPS Age Age at onset of disorder Duration of disorder Education

DES score

CTQ total score

r

p

r

p

– 0.36 0.52

– 0.002 0.001

0.38 – 0.26

0.001 – 0.031

0.48 0.40 0.33 0.29 0.41 0.33 0.31 0.31 –0.34 –0.38 –0.08 –0.15

0.001 0.001 0.005 0.002 0.001 0.005 0.008 0.010 0.004 0.001 0.509 0.227

0.31 0.34 0.29 0.06 0.19 0.07 0.12 0.12 –0.05 –0.05 –0.02 –0.07

0.009 0.004 0.025 0.644 0.125 0.546 0.327 0.327 0.668 0.667 0.883 0.543

a 4-group solution with the aim of having the opportunity to look into the distribution of both positive and negative symptoms of schizophrenia among patients in each subgroup with high and low dissociation. The subgroups derived by cluster analysis have been compared on various clinical features using one-way ANOVA and the Fisher’s exact test. For all statistical analysis, p values were two-tailed and the level of significance was set at p = 0.05.

Results

Mean age of the patients was 38.3 years (SD = 11.3, range = 19–59); 38 (54.3%) of them were women. They had 10.1 years (SD = 3.5, range = 5–20) of education on average. Mean duration of schizophrenic disorder was 13.8 (SD = 9.3, range = 1–38) years. The overall patient group had a mean CTQ score of 43.6 (range = 27.0–80.0, SD = 11.6) and a DES score of 18.1 (range = 0.0–73.9, SD = 16.6). There was no significant difference between women (mean = 18.9, SD = 18.8) and men (mean = 17.2, SD = 13.8) on DES scores (t = 0.42, d.f. = 68, p = 0.679). Female (mean = 43.7, SD = 11.9) and male (mean = 43.6, SD = 11.4) patients did not differ on CTQ scores either (t = 0.03, d.f. = 68, p = 0.974). Table 1 documents the findings from correlational analyses between various clinical measures. Age and DES scores correlated negatively. There were significant corPsychopathology 2010;43:33–40

35

relations not only between DES total scores and secondary features of DID, but also borderline personality disorder criteria, Schneiderian symptoms, extrasensory perceptions, somatic complaints, number of lifetime and current SCID diagnoses, and negative and positive symptoms of schizophrenia. There were positive correlations between CTQ and DES total scores. Among symptom groups, only borderline personality disorder criteria, extrasensory perceptions, somatic complaints, and second-

Table 2. Stepwise linear regression analysis: types of childhood

trauma as predictor of DES scores (F = 10.79, d.f. = 69, 3; p < 0.001) SE Childhood trauma scores Physical neglect 0.52 Physical abuse 0.60 Age (younger) 0.15 Constant 7.43

␤

t

p

0.28 0.28 0.37 –

2.57 2.60 3.63 2.23

0.013 1.35 (0.30–2.39) 0.011 1.56 (0.36–2.76) 0.001 0.54 (0.24–0.84) 0.029 16.58 (1.75–31.41)

OR and 95% CI

ary features of DID had significant correlations with CTQ total score, while Schneiderian symptoms did not. A stepwise linear regression analysis showed that among 6 variables (comprising age and 5 types of childhood traumas), only young age and childhood physical abuse and neglect predicted DES scores (table 2). We attempted to classify all patients through k-mean cluster analysis into 4 groups, while 11 variables entered the analysis: secondary features of DID, somatic complaints, extrasensory perceptions, Schneiderian symptoms, borderline personality disorder criteria (SCID-II), total numbers of current and lifetime SCID diagnoses, positive and negative symptom scores, total childhood trauma and DES scores (table 3). Group A (n = 13) and group B (n = 5) consisted of patients with the most robust dissociative symptomatology, such as secondary features of DID and elevated DES scores. They also had more Schneiderian symptoms, extrasensory perceptions, somatic complaints, and borderline personality disorder criteria than the remaining groups. Both groups A and B had elevated childhood trauma scores, except for emotional neglect (table 4). A significant majority of patients

Table 3. Differences between 4 patient groups derived through k-mean cluster analysis

Symptom clusters and scale scores

Schneiderian symptoms (DDIS) Somatic complaints (DDIS) Secondary features of DID (DDIS) Extrasensory perceptions (DDIS) Borderline personality disorder criteria (SCID-II) SCID diagnoses (current) SCID diagnoses (lifetime) SANS PANS DES total score Childhood trauma scores Emotional neglect Physical neglect Emotional abuse Physical abuse Sexual abuse CTQ total score Age, years Age of onset of the disorder, years Duration of the disorder, years Education, years

36

High-dissociation groups

Low-dissociation groups

1-way variance analysis

group A (n = 13)

group C (n = 10)

F p (d.f. = 3, 69)

group B (n = 5)

group D (n = 42)

7.683.2 9.887.4 5.883.3 4.582.7 4.782.9 2.881.1 3.581.3 51.7823.0 40.5815.6 40.0815.8

7.881.3 8.085.3 7.283.4 4.282.0 2.882.6 2.081.2 2.880.8 46.6814.0 106.4817.9 38.5812.4

6.182.4 2.582.2 3.582.8 1.982.6 0.380.5 2.480.7 2.681.0 80.0823.9 61.1821.5 12.5811.0

4.883.5 4.083.7 3.182.2 1.481.5 1.681.5 1.681.0 2.381.0 28.0813.7 17.9816.2 10.388.7

3.53 7.18 6.38 9.74 13.51 5.84 4.47 26.32 52.02 31.59

0.019 0.001 0.001 0.001 0.001 0.001 0.006 0.001 0.001 0.001

13.885.1 11.184.4 10.583.5 8.884.5 8.183.9 52.2810.4 32.5810.1 21.484.7 11.188.8 9.283.2

13.885.6 10.081.9 12.485.5 7.482.8 6.481.9 50.0813.4 34.6818.1 18.282.4 16.4816.3 10.283.4

13.484.3 7.682.6 6.481.8 5.580.8 5.481.0 38.387.9 36.4813.6 23.687.7 12.888.8 9.083.7

12.983.8 8.083.1 8.184.3 6.382.5 6.182.1 41.5811.1 41.089.7 26.488.6 14.189.2 10.683.5

0.17 3.67 3.59 3.37 2.84 4.72 2.33 2.73 0.50 0.96

0.914 0.016 0.018 0.024 0.044 0.005 0.083 0.051 0.685 0.418



who fit the DSM-IV criteria for borderline personality disorder were in the dissociative group (table 4). Very few patients had a current or lifetime diagnosis of PTSD or substance abuse. While the overall number of psychiatric comorbidities was correlated with DES scores, none of the comorbid psychiatric diagnoses was associated exclusively with the dissociative subgroup. Although positive symptoms of schizophrenia predominated in group B, group A was characterized by both positive and negative symptoms. Group A had the highest scores on childhood sexual and physical abuse. They had more diagnoses of concurrent mood and anxiety disorder than group B. On the other hand, group B had the highest scores on childhood emotional abuse. There was no relationship between traditional subtypes of schizophrenia and the subgroups derived by cluster analysis (table 4), and gender also was not related to any of them.

Discussion

As shown by correlations between symptoms and mental health history items, and an independent cluster analysis, the present study documented the existence of a dissociative subgroup among schizophrenic patients. Notwithstanding the need for further research to establish its validity, this finding supports a dissociative subtype of schizophrenia as proposed by Ross [22]. This subgroup did not overlap with any of the classical subtypes of schizophrenia (table 4). The relationship of positive and negative symptoms of schizophrenia with a dissociative subtype was also heterogenous (table 3). Thus, the dissociative subtype of schizophrenia represents a paradigm different from previous ones. Three previous studies documented that patients with schizophrenic disorder and a high level of dissociation report childhood traumas more frequently than non-dissociative schizophrenic patients [8, 10, 21]. Indeed, there were significant correlations between DES and CTQ total scores in the present study. There were also significant correlations between CTQ total score and secondary

Table 4. Differences between 4 patient groups derived through k-mean cluster analysis

High-dissociation groups

Low-dissociation groups

group A (n = 13)

group B (n = 5)

group C (n = 10)

group D (n = 42)

n

%

n

%

n

%

n

%

Subtypes of schizophrenia (SCID-II) Paranoid Catatonic Disorganized Undifferentiated Residual

6 0 2 3 2

46.2 0.0 15.4 23.1 15.4

2 0 2 1 0

40.0 0.0 40.0 10.0 0.0

4 0 2 1 3

40.0 0.0 20.0 10.0 30.0

18 1 3 7 13

42.9 2.4 7.1 16.7 31.0

1.000 1.000 0.102 0.873 0.453

Psychiatric Comorbidity (SCID-II) Any adjustment disorder (current) Any adjustment disorder (lifetime) Any somatoform disorder (current) Any somatoform disorder (lifetime) Any anxiety disorder (current) Any anxiety disorder (lifetime) Any mood disorder (current) Any mood disorder (lifetime) PTSD (current) PTSD (lifetime) Substance use (current) Substance use (lifetime) Borderline personality disorder

4 4 2 2 8 9 8 11 1 1 0 1 7

30.8 30.8 15.4 15.4 61.5 69.2 61.5 84.6 7.7 7.7 0.0 7.7 53.8

2 2 1 1 0 2 1 3 0 0 1 0 2

40.0 40.0 20.0 20.0 0.0 40.0 20.0 60.0 0.0 0.0 20.0 0.0 40.0

3 3 1 2 4 4 6 7 0 0 0 0 0

30.0 30.0 10.0 20.0 40.0 40.0 60.0 70.0 0.0 0.0 0.0 0.0 0.0

7 14 0 0 10 15 8 24 0 2 0 4 2

16.7 33.3 0.0 0.0 23.8 35.7 19.0 57.1 0.0 4.8 0.0 9.5 4.8

0.369 1.000 0.023 0.023 0.027 0.202 0.005 0.334 0.400 0.790 1.000 0.877 0.001

8

61.5

3

60.0

2

20.0

25

59.5

0.135

Female



Fisher’s exact test p

37

symptoms of DID alongside somatic complaints, extrasensory perceptions, and borderline personality disorder criteria (table 2), which are known to be part of dissociative disorders [38]. However, CTQ scores were not related to positive or negative symptoms of schizophrenia and, in contrast to a previous study [41], neither to Schneiderian symptoms. Unlike childhood trauma scores, dissociative experiences were correlated with negative and positive symptoms of schizophrenia and Schneiderian symptoms as well (table 1). Thus, the present study suggests that childhood trauma is related to concurrent dissociation rather than to core features of schizophrenia, while there was a more proximal relationship between schizophrenia and dissociation [29]. Representing a nosological fragmentation, high general psychiatric comorbidity is a phenomenon observed among traumatized psychiatric populations in particular [42]. In accordance with this observation, dissociation scores were correlated with total number of current and lifetime comorbid psychiatric disorders, while none of the comorbid DSM-IV [30] axis-I diagnoses was associated exclusively with the dissociative subtype of schizophrenia. Nevertheless, a statistically significant number of patients with borderline personality disorder diagnosis belonged to the high-dissociation group (table 4). Previous studies documented a large overlap between borderline personality disorder and dissociative disorders, including high frequencies of reported childhood trauma [43]. In a previous study on patients with schizophrenia, higher levels of borderline traits were uniquely related to the report of childhood sexual abuse [44]. It is possible that borderline personality disorder criteria represent a trauma-related symptom pattern among patients with schizophrenic disorder rather than a personality disorder per se. In the present study, young age and childhood physical abuse and neglect predicted dissociation. Dissociative experiences are known to be negatively correlated with age, both in clinical and non-clinical populations [36, 37]. While being the most frequently reported types of childhood adverse experiences in Turkey [45], physical abuse and neglect also may start to take effect at an earlier age compared to other types of childhood trauma. In support of its culture-free impact, childhood physical neglect was predictor of adult dissociation among schizophrenic patients in a recent study from Germany as well [46]. There were no gender differences on childhood trauma and dissociation scores, pointing to a common factor affecting both genders in context of a severe mental illness.

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Significant overlap between any of the disorders may arise for several reasons. In addition to shared risk factors or fuzzy boundaries between the diagnoses, one of the disorders may itself be a risk factor for the other. While the introduction of a dissociative subtype of schizophrenia has advantages in terms of clinical utility, it does not necessarily suggest the validity of a categorical model and the same solution may fit with a dimensional approach as well. Notwithstanding the possibility of a clinical spectrum from dissociation to schizophrenia either, we also consider a duality (interaction) model to explain complex co-existence of 2 distinct but concurrent or subsequent psychopathologies as a possibility [47]. In fact, the notion of a relatively healthy part of personality not affected by prevailing psychopathology is not new in psychiatry, including Bleuler’s original conceptualization of schizophrenia as ‘split mind’ (or splitting of psychological functions) and in contrast to the ‘dementia praecox’ of Kraepelin [48]. Most recently, this notion has been revived under the rubric of the structural dissociation model of personality as its modern version [49, 50]. In application of Bleuler’s notion about a healthy part onto the structural dissociation model of personality, the duality model assumes coexistence and interaction between two qualitatively distinct psychopathologies depending on whether dissociation functions as a source of resilience against, a risk factor for, or a response to a schizophrenic disorder. One of the assumptions is that dissociation may function as a defense against or a facade before an intrapsychic threat of schizophrenic psychopathology becomes manifest, historically described in diverse ways depending on prevailing conceptualizations such as pseudoneurotic schizophrenia [51]. Although this defense may prevent the progression of, or encapsulate, the severe psychopathology for some subjects, it may make the condition more complex for others and even constitutes the pathway leading to a severer mental illness [52]. In addition, coping with the lifelong experience of having a chronic and devastating mental illness may require adaptive dissociative mechanisms, such as denial of the disorder, social detachment, mental absorption, change of perception of the self and the environment, and identity disturbances. A similar interaction model has been proposed for PTSD and severe mental illness by several authors [53, 54]. A psychotic episode can itself be a cause of PTSD as well which may even lead to suicide attempts [55]. Although in its infancy, we hope that the duality hypothesis may serve as a starting point for further research in this field of complex comorbidity. Sar /Taycan /Bolat /Özmen /Duran / Öztürk /Ertem-Vehid

The present study has several limitations. First of all, the study group consisted of chronic patients with longterm psychiatric history. Moreover, all patients were receiving neuroleptic drug treatment and the study assessment was conducted after a stabilization phase for some of them. A study on first-episode schizophrenia and medication-free patients may lead to different results. Second, the assessment instruments were not designed specifically for identifying qualitative differences between symptoms which are common in both disorders, e.g. Schneiderian symptoms and hallucinations [56]. Third, childhood trauma reports are of retrospective nature; thus, they are subject to possible reinterpretation and are also susceptible to distortions by psychopathology. However, this may happen in both directions. As aversive contents, childhood traumas can be subject to minimization or denial as well [11]. Fourth, in consideration of the multivariate statistical method used in this study, the relatively small sample size may also be considered as a limitation. Nevertheless, k-means clustering does not involve any significance testing, so issues of

power and sample size do not arise [57]. The only sample size issue is whether or not the sample is representative enough to allow generalizations to be made. Thus, as the sample is representative only for chronic patients, the present study does not allow generalizations to patients in early stages of the disorder.

Conclusions

In support of an earlier proposal for a dissociative subtype of schizophrenia, the present study documented that there is a subgroup of schizophrenic patients who have dissociative symptoms and childhood trauma history more frequently than the remaining patients. Overall, childhood trauma seems to be related to concurrent dissociation rather than to core features of schizophrenic disorder. The complex relationship between 2 psychopathologies and/or childhood trauma requires further study based on diverse models of psychopathology.

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