Dissociative part-dependent resting-state activity in dissociative identity disorder: a controlled FMRI perfusion study

A cross-sectional survey on French psychiatrists' knowledge and perceptions of dissociative identity disorder

OBJECTIVE

The aim of this study was to determine French psychiatrists' level of general knowledge about dissociative identity disorder and to evaluate their perceptions of this condition.

METHODS

In this study, French psychiatrists were invited by e-mail to answer an online survey. The questionnaire asked about their general knowledge and perceptions of dissociative identity disorder.

RESULTS

We received 924 answers including 582 complete questionnaires. The survey revealed that almost two-thirds (60.8%) of psychiatrists working in France had never received any training on dissociative disorders and 62% had never managed patients suffering from dissociative identity disorder. Only 19.5% of them claimed to believe unreservedly in the existence of the diagnosis of dissociative identity disorder. The psychiatrists' confidence in diagnosing or treating dissociative identity disorder was low (mean confidence in diagnosis: 3.32 out of 10 (SD 1.89), mean confidence in treatment: 3.1 out of 10 (SD 1.68)). Fifty percent believed that dissociative identity disorder is an entity created by cinema, medias or social networks. Seventy-seven point seven percent thought that confusion with borderline personality disorder is possible, and 41.3% with schizophrenia.

CONCLUSION

In France, there is a lack of training and knowledge about dissociative identity disorder, as well as persistent skepticism about the validity of the diagnosis. Specific training seems essential for a better understanding of dissociative identity disorder.

Hierarchical consciousness: the Nested Observer Windows model

Foremost in our experience is the intuition that we possess a unified conscious experience. However, many observations run counter to this intuition: we experience paralyzing indecision when faced with two appealing behavioral choices, we simultaneously hold contradictory beliefs, and the content of our thought is often characterized by an internal debate. Here, we propose the Nested Observer Windows (NOW) Model, a framework for hierarchical consciousness wherein information processed across many spatiotemporal scales of the brain feeds into subjective experience. The model likens the mind to a hierarchy of nested mosaic tiles-where an image is composed of mosaic tiles, and each of these tiles is itself an image composed of mosaic tiles. Unitary consciousness exists at the apex of this nested hierarchy where perceptual constructs become fully integrated and complex behaviors are initiated via abstract commands. We define an observer window as a spatially and temporally constrained system within which information is integrated, e.g. in functional brain regions and neurons. Three principles from the signal analysis of electrical activity describe the nested hierarchy and generate testable predictions. First, nested observer windows disseminate information across spatiotemporal scales with cross-frequency coupling. Second, observer windows are characterized by a high degree of internal synchrony (with zero phase lag). Third, observer windows at the same spatiotemporal level share information with each other through coherence (with non-zero phase lag). The theoretical framework of the NOW Model accounts for a wide range of subjective experiences and a novel approach for integrating prominent theories of consciousness.

Dissociative Identity Disorder: A Review of Research From 2011 to 2021

ABSTRACT

Dissociative identity disorder (DID) has historically been one of the most controversial topics in the study of psychopathology. Building on a previous review of empirical research on DID from 2000 to 2010, the present review examined DID research from 2011 to 2021. The research output included 56 case studies and 104 empirical studies. Within the empirical studies, approximately 1354 new cases of DID emerged, which resulted in an average samples of approximately 20. Reanalysis of previous samples was standard in the literature with only 40% of reported cases being new. Studies emerged from dozens of countries across the world, but the majority of cases were from Western counties, especially the United States. Diagnosis primarily relied upon validated measures, but 74% of all new cases came from six research groups. Overall, research on DID is steady but methodologically limited in ways that make generalization, especially about etiology, difficult.

Identity state-dependent self-relevance and emotional intensity ratings of words in dissociative identity disorder: A controlled longitudinal study

INTRODUCTION

Dissociative identity disorder (DID) is characterized by, among others, amnesic episodes and the recurrence of different dissociative identity states. While consistently observed in clinical settings, to our knowledge, no controlled research study has shown the degree to which different identity states report autobiographical knowledge over time. Hence, the current study investigates self-relevance and emotional intensity ratings of words longitudinally.

METHODS

Data of 46 participants were included: 13 individuals with DID, 11 DID-simulating actors, and a control group of 22 paired individuals. Individuals with DID and DID simulators participated once in the neutral identity state (NIS) and once in the trauma-related dissociative identity state (TIS). The control group paired 11 healthy controls with 11 participants with posttraumatic stress disorder (PTSD) as a NIS-TIS pair. Self-relevance ratings of different word types were collected in a baseline and a follow-up session, on average 6 weeks apart. A mixed ANOVA design was used to assess the effects of group, session, word type, and dissociative identity state.

RESULTS

All participants in TIS and individuals with DID in NIS rated self-relevant trauma-related words more negatively. In the NIS, the control group rated self-relevant trauma-related words as less negative, whereas the ratings of simulating actors were intermediate. There was no group-dependent longitudinal effect for intensity ratings.

CONCLUSIONS

This study was the first to confirm clinical observations that self-relevant and emotional processing are different between individuals with DID and controls, but consistent over time. Actors were unable to perfectly simulate DID. The finding that ratings of self-relevant trauma-related words differ between subgroups as included in the study is in line with clinical observations.

Assessing malingering and personality styles in dissociative identity disorder: a case study

Dissociative Identity Disorder (DID), formerly Multiple Personality Disorder, involves two or more distinct identities controlling behaviour, stemming from trauma-related dissociation. Understanding DID's cognitive, neural, and psychometric aspects remains a challenge, especially in distinguishing genuine cases from malingering. We present a case of a DID patient with nine identities, evaluated to rule out malingering. Using the Millon Index of Personality Styles, we assessed the primary and two alternate identities, revealing marked differences. High consistency scores support validity. We suggest employing personality inventories beyond symptomatology to characterise dissociative identities' consistency and adaptation styles, aiding in malingering assessments in future studies.

The integrative process promoted by EMDR in dissociative disorders: neurobiological mechanisms, psychometric tools, and intervention efficacy on the psychological impact of the COVID-19 pandemic

Dissociative disorders (DDs) are characterized by a discontinuity in the normal integration of consciousness, memory, identity, emotion, perception, bodily representation, motor control, and action. The life-threatening coronavirus disease 2019 (COVID-19) pandemic has been identified as a potentially traumatic event and may produce a wide range of mental health problems, such as depression, anxiety disorders, sleep disorders, and DD, stemming from pandemic-related events, such as sickness, isolation, losing loved ones, and fear for one's life. In our conceptual analysis, we introduce the contribution of the structural dissociation of personality (SDP) theory and polyvagal theory to the conceptualization of the COVID-19 pandemic-triggered DD and the importance of assessing perceived safety in DD through neurophysiologically informed psychometric tools. In addition, we analyzed the contribution of eye movement desensitization and reprocessing (EMDR) to the treatment of the COVID-19 pandemic-triggered DD and suggest possible neurobiological mechanisms of action of the EMDR. In particular, we propose that, through slow eye movements, the EMDR may promote an initial non-rapid-eye-movement sleep stage 1-like activity, a subsequent access to a slow-wave sleep activity, and an oxytocinergic neurotransmission that, in turn, may foster the functional coupling between paraventricular nucleus and both sympathetic and parasympathetic cardioinhibitory nuclei. Neurophysiologically informed psychometric tools for safety evaluation in DDs are discussed. Furthermore, clinical and public health implications are considered, combining the EMDR, SDP theory, and polyvagal conceptualizations in light of the potential dissociative symptomatology triggered by the COVID-19 pandemic.

The Missing Ingredient: How Misogyny and the Patriarchy Sabotage our Clinical Practice and Research

Discussing massive, unrelenting trauma, especially during a global pandemic, when the threat is not only personally affecting you, but also everyone else, is not an easy thing to do. We can see the consequences of two years of being locked inside. People's trauma responses literally came flooding out. It seems that the pandemic tipped us over an abyss that is hard to comprehend. In so many countries there are protests, laws rolling back basic human rights, the threat of fascism, and actual war. There seems to be widespread governmental corruption that cannot stop the favouritism of those who have wealth, and perpetually admonish those who do not. Our world seems very unstable. Change is deeply desired. Yet, this instability is predictable. It is predictable because the systems that created the structures that "run and rule" us are fundamentally destructive and violent. In never-ending ways, the only way that change happens is by utilizing violence as the only way to achieve change. This is the legacy of patriarchy. A system that not only is ruled by one group of people but also tends to be controlled by a very specific type of person. It is a system that cultivates human cruelty, selfishness, and violence. It is a system that is managed by those who do the "best" in violence. Most of us do not work this way but are forced to live this way because of the belief that humans are innately violent, selfish, and self-serving; a myth based on the traumatic reaction of fight. It is a dissociated, relational injury that is a direct result of not having our mothers and fathers able to be mothers and fathers. It is formed in misogyny. There are ways to heal, if one can comprehend what misogyny does to human beings, and what we would be like in its absence.

A neurostructural biomarker of dissociative amnesia: a hippocampal study in dissociative identity disorder

BACKGROUND

Little is known about the neural correlates of dissociative amnesia, a transdiagnostic symptom mostly present in the dissociative disorders and core characteristic of dissociative identity disorder (DID). Given the vital role of the hippocampus in memory, a prime candidate for investigation is whether total and/or subfield hippocampal volume can serve as biological markers of dissociative amnesia.

METHODS

A total of 75 women, 32 with DID and 43 matched healthy controls (HC), underwent structural magnetic resonance imaging (MRI). Using Freesurfer (version 6.0), volumes were extracted for bilateral global hippocampus, cornu ammonis (CA) 1-4, the granule cell molecular layer of the dentate gyrus (GC-ML-DG), fimbria, hippocampal-amygdaloid transition area (HATA), parasubiculum, presubiculum and subiculum. Analyses of covariance showed volumetric differences between DID and HC. Partial correlations exhibited relationships between the three factors of the dissociative experience scale scores (dissociative amnesia, absorption, depersonalisation/derealisation) and traumatisation measures with hippocampal global and subfield volumes.

RESULTS

Hippocampal volumes were found to be smaller in DID as compared with HC in bilateral global hippocampus and bilateral CA1, right CA4, right GC-ML-DG, and left presubiculum. Dissociative amnesia was the only dissociative symptom that correlated uniquely and significantly with reduced bilateral hippocampal CA1 subfield volumes. Regarding traumatisation, only emotional neglect correlated negatively with bilateral global hippocampus, bilateral CA1, CA4 and GC-ML-DG, and right CA3.

CONCLUSION

We propose decreased CA1 volume as a biomarker for dissociative amnesia. We also propose that traumatisation, specifically emotional neglect, is interlinked with dissociative amnesia in having a detrimental effect on hippocampal volume.

Deconstructing dissociation: a triple network model of trauma-related dissociation and its subtypes

Trauma-related pathological dissociation is characterized by disruptions in one's sense of self, perceptual, and affective experience. Dissociation and its trauma-related antecedents disproportionately impact women. However, despite the gender-related prevalence and high individual and societal costs, dissociation remains widely underappreciated in clinical practice. Moreover, dissociation lacks a synthesized neurobiological model across its subtypes. Leveraging the Triple Network Model of psychopathology, we sought to parse heterogeneity in dissociative experience by examining functional connectivity of three core neurocognitive networks as related to: (1) the dimensional dissociation subtypes of depersonalization/derealization and partially-dissociated intrusions; and, (2) the diagnostic category of dissociative identity disorder (DID). Participants were 91 women with and without: a history of childhood trauma, current posttraumatic stress disorder (PTSD), and varied levels of dissociation. Participants provided clinical data about dissociation, PTSD symptoms, childhood maltreatment history, and completed a resting-state functional magnetic resonance imaging scan. We used a novel statistical approach to assess both overlapping and unique contributions of dissociation subtypes. Covarying for age, childhood maltreatment and PTSD severity, we found dissociation was linked to hyperconnectivity within central executive (CEN), default (DN), and salience networks (SN), and decreased connectivity of CEN and SN with other areas. Moreover, we isolated unique connectivity markers associated with depersonalization/derealization in CEN and DN, to partially-dissociated intrusions in CEN, and to DID in CEN. This suggests dissociation subtypes have robust functional connectivity signatures that may serve as targets for PTSD/DID treatment engagement. Our findings underscore dissociation assessment as crucial in clinical care, in particular, to reduce gender-related health disparities.

The brain-body disconnect: A somatic sensory basis for trauma-related disorders

Although the manifestation of trauma in the body is a phenomenon well-endorsed by clinicians and traumatized individuals, the neurobiological underpinnings of this manifestation remain unclear. The notion of somatic sensory processing, which encompasses vestibular and somatosensory processing and relates to the sensory systems concerned with how the physical body exists in and relates to physical space, is introduced as a major contributor to overall regulatory, social-emotional, and self-referential functioning. From a phylogenetically and ontogenetically informed perspective, trauma-related symptomology is conceptualized to be grounded in brainstem-level somatic sensory processing dysfunction and its cascading influences on physiological arousal modulation, affect regulation, and higher-order capacities. Lastly, we introduce a novel hierarchical model bridging somatic sensory processes with limbic and neocortical mechanisms regulating an individual's emotional experience and sense of a relational, agentive self. This model provides a working framework for the neurobiologically informed assessment and treatment of trauma-related conditions from a somatic sensory processing perspective.

Neurostructural brain imaging study of trait dissociation in healthy children

BACKGROUND

Trait dissociation has not been examined from a structural human brain mapping perspective in healthy adults or children. Non-pathological dissociation shares some features with daydreaming and mind-wandering, but also involves subtle disruptions in affect and autobiographical memory.

AIMS

To identify neurostructural biomarkers of trait dissociation in healthy children.

METHOD

Typically developing 9- to 15-year-olds (n = 180) without psychological or behavioural disorders were enrolled in the Developmental Chronnecto-Genomics (DevCoG) study of healthy brain development and completed psychological assessments of trauma exposure and dissociation, along with a structural T₁-weighted magnetic resonance imaging. We conducted univariate ANCOVA generalised linear models for each region of the default mode network examining the effects of trait dissociation, including scanner site, age, gender and trauma as covariates and correcting for multiple comparison.

RESULTS

We found that the precuneus was significantly larger in children with higher levels of trait dissociation but this was not related to trauma exposure. The inferior parietal volume was smaller in children with higher levels of trauma but was not related to dissociation. No other regions of interest, including frontal and limbic structures, were significantly related to trait dissociation even before multiple comparison correction.

CONCLUSIONS

Trait dissociation reflects subtle cognitive disruptions worthy of study in healthy people and warrants study as a potential risk factor for psychopathology. This neurostructural study of trait dissociation in healthy children identified the precuneus as an essential brain region to consider in future dissociation research.

Functional Neuroimaging in Dissociative Disorders: A Systematic Review

Background: Dissociative disorders encompass loss of integration in essential functions such as memory, consciousness, perception, motor control, and identity. Nevertheless, neuroimaging studies, albeit scarce, have suggested the existence of particular brain activation patterns in patients belonging to this diagnostic category. The aim of this review is to identify the main functional neuroimaging correlates of dissociative disorders. Methods: we searched the PubMed database to identify functional neuroimaging studies conducted on subjects with a diagnosis of a dissociative disorder, following the PRISMA guidelines. In the end, we included 13 studies in this systematic review, conducted on 51 patients with dissociative identity disorder (DID), 28 subjects affected by depersonalization disorder, 24 with dissociative amnesia, and 6 with other or not specified dissociative disorders. Results: Prefrontal cortex dysfunction seems prominent. In addition, changes in the functional neural network of the caudate are related to alterations of identity state and maintenance of an altered mental status in DID. Another role in DID seems to be played by a dysfunction of the anterior cingulate gyrus. Other regions, including parietal, temporal, and insular cortices, and subcortical areas were reported to be dysfunctional in dissociative disorders. Conclusions: Prefrontal dysfunction is frequently reported in dissociative disorders. Functional changes in other cortical and subcortical areas can be correlated with these diagnoses. Further studies are needed to clarify the neurofunctional correlations of each dissociative disorder in affected patients, in order to identify better tailored treatments.

Dissociative identity state-dependent working memory in dissociative identity disorder: a controlled functional magnetic resonance imaging study

BACKGROUND

Memory function is at the core of the psychopathology of dissociative identity disorder (DID), but little is known about its psychobiological correlates.

AIMS

This study aims to investigate whether memory function in DID differs between dissociative identity states.

METHOD

Behavioural data and neural activation patterns were assessed in 92 sessions during an n-back working memory task. Participants were people with genuine diagnosed DID (n = 14), DID-simulating controls (n = 16) and a paired control group (post-traumatic stress disorder (n = 16), healthy controls (n = 16)). Both DID groups participated as authentic or simulated neutral and trauma-related identity states. Reaction times and errors of omission were analysed with repeated measures ANOVA. Working memory neural activation (main working memory and linear load) was investigated for effects of identity state, participant group and their interaction.

RESULTS

Identity state-dependent behavioural performance and neural activation was found. DID simulators made fewer errors of omission than those with genuine DID. Regarding the prefrontal parietal network, main working memory in the left frontal pole and ventrolateral prefrontal cortex (Brodmann area 44) was activated in all three simulated neutral states, and in trauma-related identity states of DID simulators, but not those with genuine DID or post-traumatic stress disorder; for linear load, trauma-related identity states of those with genuine DID did not engage the parietal regions.

CONCLUSIONS

Behavioural performance and neural activation patterns related to working memory in DID are dependent on the dissociative identities involved. The narrowed consciousness of trauma-related identity states, with a proneness to re-experiencing traumatising events, may relate to poorer working memory functioning.

Functional connectivity changes in the delta frequency band following trauma treatment in complex trauma and dissociative disorder patients

OBJECTIVE

Phase-oriented trauma treatment is efficacious in the treatment of complex trauma and dissociative disorder patients. However, the neural correlates of this therapeutic effect are not yet well-understood. In the current study we investigated whether patients show a strengthening in functional network connectivity in the delta frequency band (1-3.5 Hz) over the course of phase-oriented inpatient trauma treatment while they performed an emotion regulation task. Further, we examined whether neural changes were associated with symptom reduction and improvement in emotion regulation skills.

METHODS

Before and after 8 weeks of treatment, electroencephalography (EEG) was acquired in patients (n = 28) with a complex posttraumatic stress disorder (cPTSD) or complex dissociative disorder (CDD). They also completed clinical and emotion regulation questionnaires. To delimit data variability, patients participated as one dissociative part that is referred to as Apparently Normal Part (ANP). Patients' data were compared to a matched healthy control croup (n = 38), also measured twice.

RESULTS

Prior to treatment, functional connectivity was significantly lower in patients compared to controls during cognitive reappraisal of unpleasant pictures and passive viewing of unpleasant and neutral pictures. These hypoconnected networks largely overlapped with networks typically activated during the recall of (emotional) autobiographical memories. Functional connectivity strength within these networks significantly increased following treatment and was comparable to controls. Patients showed symptom reduction across various clinical domains and improvement in the use of cognitive reappraisal as emotion regulation strategy. Treatment-related network normalizations were not related to changes in questionnaire data.

CONCLUSION

Phase-oriented treatment may strengthen connections between regions that are activated during autobiographical recall. These findings encourage further investigation of this circuitry as a therapeutic target in cPTSD and CDD patients.

CLINIAL TRIAL REGISTRATION

www.ClinicalTrials.gov, identifier: NCT02459340, https://www.kofam.ch/de/studienportal/suche/149284/studie/26681.

Thalamic volume and fear extinction interact to predict acute posttraumatic stress severity

Posttraumatic stress disorder (PTSD) is associated with lower gray matter volume (GMV) in brain regions critical for extinction of learned threat. However, relationships among volume, extinction learning, and PTSD symptom development remain unclear. We investigated subcortical brain volumes in regions supporting extinction learning and fear-potentiated startle (FPS) to understand brain-behavior interactions that may impact PTSD symptom development in recently traumatized individuals. Participants (N = 99) completed magnetic resonance imaging and threat conditioning two weeks following trauma exposure as part of a multisite observational study to understand the neuropsychiatric effects of trauma (AURORA Study). Participants completed self-assessments of PTSD (PTSD Checklist for DSM-5; PCL-5), dissociation, and depression symptoms two- and eight-weeks post-trauma. We completed multiple regressions to investigate relationships between FPS during late extinction, GMV, and PTSD symptom development. The interaction between thalamic GMV and FPS during late extinction at two weeks post-trauma predicted PCL-5 scores eight weeks (t (75) = 2.49, β = 0.28, p = 0.015) post-trauma. Higher FPS predicted higher PCL-5 scores in the setting of increased thalamic GMV. Meanwhile, lower FPS also predicted higher PCL-5 scores in the setting of decreased thalamic GMV. Thalamic GMV and FPS interactions also predicted posttraumatic dissociative and depressive symptoms. Amygdala and hippocampus GMV by FPS interactions were not associated with posttraumatic symptom development. Taken together, thalamic GMV and FPS during late extinction interact to contribute to adverse posttraumatic neuropsychiatric outcomes. Multimodal assessments soon after trauma have the potential to distinguish key phenotypes vulnerable to posttraumatic neuropsychiatric outcomes.

Resting-state functional connectivity in patients with a complex PTSD or complex dissociative disorder before and after inpatient trauma treatment

INTRODUCTION

Recent research suggests that traumatized patients are characterized by disrupted resting-state functional connectivity. We examined whether neural networks involved in resting-state change over the course of a phase-oriented inpatient treatment for complex traumatized and dissociative disorder patients. We also investigated associations between these network alterations and clinical symptoms and emotion regulation skills.

METHODS

Pre- and post-treatment, electroencephalography (EEG) was recorded during resting-state in patients (n = 23) with a complex dissociative disorder (CDD) or complex posttraumatic stress disorder (cPTSD). Patients also completed clinical and emotion regulation questionnaires. To reduce variance in the collected data, patients were exclusively tested as one prototypical dissociative part referred to as Apparently Normal Part (ANP). Functional network connectivity was examined and compared with a matched healthy control group (n = 37), also measured twice.

RESULTS

Prior to treatment and compared with controls, patients had a significantly lower functional connectivity strength within eyes-open and eyes-closed resting-state networks in the theta and alpha frequency band. Following treatment, functional connectivity strength within these networks was comparable to the control group and comprised areas belonging to the default mode network (DMN) and prefrontal as well as anterior cingulate control regions. Treatment-related network normalizations in the theta frequency band were associated with a self-reported increase in the use of cognitive reappraisal strategies and reduction in emotion regulation difficulties.

CONCLUSION

Phase-oriented trauma treatment can strengthen resting-state network connectivity and can increase the capacity of complex traumatized and dissociative patients as ANP to handle emotional challenges effectively.

Altered spontaneous brain activity in patients with childhood absence epilepsy: associations with treatment effects

The study aims to detect resting-state functional MRI (RS-fMRI) changes and their relationships with the clinical treatment effects of anti-epileptic drugs (AEDs) for patients with childhood absence epilepsy (CAE) using the fractional amplitude of low-frequency fluctuation (fALFF). RS-fMRI data from 30 CAE patients were collected and compared with findings from 30 healthy controls (HCs) with matched sex and age. Patients were treated with first-line AEDs for 46.2 months before undergoing a second RS-fMRI scan. fALFF data were processed using DPABI and SPM12 software. Compared with the HCs, CAE patients at baseline showed increased fALFF in anterior cingulate cortex, inferior parietal lobule, inferior frontal lobule, supplementary motor area and reduced fALFF in putamen and thalamus. At follow-up, the fALFF showed a clear rebound which indicated a normalization of spontaneous brain activities in these regions. In addition, the fALFF changes within thalamus showed significant positive correlation with the seizure frequency improvements. Our results suggest that specific cortical and subcortical regions are involved in seizure generation and the neurological impairments found in CAE children and might shed new light about the AEDs effects on CAE patients.

The utility of the Structured Inventory of Malingered Symptomatology for distinguishing individuals with Dissociative Identity Disorder (DID) from DID simulators and healthy controls

BACKGROUND

Individuals with dissociative identity disorder (DID) have complex symptoms consistent with severe traumatic reactions. Clinicians and forensic assessors are challenged by distinguishing symptom exaggeration and feigning from genuine symptoms among these individuals. This task may be aided by administering validity measures.

OBJECTIVE

This study aimed to document how individuals with DID score on the Structured Inventory of Malingered Symptomatology (SIMS). The second objective was to compare coached DID simulators and healthy controls to DID patients on the SIMS's total score and subscales. The third objective was to examine the utility rates of the SIMS in distinguishing simulated DID from clinically diagnosed DID.

METHOD

We compared SIMS data gathered from participants from two Dutch sites, one Swiss site and one U.S. site. Sixty-three DID patients were compared to 77 coached DID simulators and 64 healthy controls on the SIMS. A multivariate analysis compared the groups on the SIMS total scores and subscales, and post-hoc Games Howell tests and univariate ANOVAs examined differences between the groups. Utility statistics assessed the accuracy of the SIMS in distinguishing clinical from simulated DID.

RESULTS

DID simulators scored significantly higher than DID individuals and healthy controls on every SIMS subscale as well as the total score. The majority (85.7%) of the individuals with DID scored above the cut-off, which is typically interpreted as indicative of possible symptom exaggeration. DID individuals scored higher than the healthy controls on every subscale except Low Intelligence, even after controlling for dissociation. The subscales and items most frequently endorsed by the DID group are consistent with symptoms associated with complex trauma exposure and dissociative reactions. The SIMS total score had a sensitivity of 96% but an unacceptably low specificity of 14%.

CONCLUSIONS

The findings indicate that the instrument is not accurate in assessing potential symptom exaggeration or feigning in DID.

Biomarkers of Pathological Dissociation: A Systematic Review

Pathological dissociation is a severe, debilitating and transdiagnostic psychiatric symptom. This review identifies biomarkers of pathological dissociation in a transdiagnostic manner to recommend the most promising research and treatment pathways in support of the precision medicine framework. A total of 205 unique studies that met inclusion criteria were included. Studies were divided into four biomarker categories, namely neuroimaging, psychobiological, psychophysiological and genetic biomarkers. The dorsomedial and dorsolateral prefrontal cortex, bilateral superior frontal regions, (anterior) cingulate, posterior association areas and basal ganglia are identified as neurofunctional biomarkers of pathological dissociation and decreased hippocampal, basal ganglia and thalamic volumes as neurostructural biomarkers. Increased oxytocin and prolactin and decreased tumor necrosis factor alpha (TNF-α) are identified as psychobiological markers. Psychophysiological biomarkers, including blood pressure, heart rate and skin conductance, were inconclusive. For the genetic biomarker category studies related to dissociation were limited and no clear directionality of effect was found to warrant identification of a genetic biomarker. Recommendations for future research pathways and possible clinical applicability are provided.

A novel theory on the predictive value of variation in the β-endorphin system on the risk and severity of PTSD

Despite growing interest in genetic and psychosocial indicators of heightened susceptibility to posttraumatic stress disorder (PTSD), a predictive model, which explains why some individuals develop PTSD in response to life-threatening traumatic events, while others, when faced with the same or similar experiences, do not, has thus far remained out of reach. In this paper, we review the literature on gene-environment interactions in β-endorphin system functioning with regard to PTSD and suggest that variation, both genetic and with regard to environmental stimuli, in systems which, like the β-endorphin system, distort human perception of life-threatening traumatic experiences may account for some of the variance in resilience to the disorder. Given the role of β-endorphin in both social connections and physical exercise, this becomes especially relevant with regard to military selection, training, and leadership processes.

Resolution of Dissociated Ego States Relieves Flashback-Related Symptoms in Combat-Related PTSD: A Brief Mindfulness Based Intervention

A novel understanding and therapeutic approach to the treatment of PTSD-related flashback triggers are described. Triggered responses are conceptualized as the result of latent dissociative structures of neural organization and psychodynamic functioning activated by current events. The dissociative structure - here described as a dissociated ego state (DES) - reflects a fracturing of executive functioning resulting in a delimited aspect of self that is not under cognitive control or subject to cognitive inhibition by the self of daily experience, and is the psychological construct behind intrusive PTSD symptoms. Use of a mindful attentional state permits regulated access to the DES (therapeutic engagement without risk of emotional dysregulation) so that dissociated cognitive resources can be recovered and the dissociated structure deactivated. This may relieve maladaptive responses and behaviors associated with the DES in a profound and durable way, without the need for exposure to or recovery of traumatic memories. Based on this understanding, a 9-step intervention is introduced with a case example of a Vietnam veteran suffering PTSD symptoms for 49 years with significant gains maintained at 21 months follow up. These findings demonstrate rapid and durable resolution of chronic PTSD symptoms through a mindfulness-based approach that focused on deactivation of dissociated ego states, in contrast to targeting trauma memories. If proven efficacious, this novel approach may result in reduced treatment costs and improved outcomes for veterans suffering with PTSD.

Sleep, trauma, fantasy and cognition in dissociative identity disorder, post-traumatic stress disorder and healthy controls: a replication and extension study

Background: Two aetiology models for dissociative identity disorder (DID) have been proposed, namely a childhood Trauma Model and an iatrogenic or Fantasy model. A recent study indicated that sleep disturbances underlie dissociative symptomatology. Objective: Our current study aims to test whether this finding can be replicated in an independent sample and to investigate if this finding still holds after correcting for childhood and adult traumatization. An experimental working memory task is included to investigate how sleep disturbance, traumatization, dissociation, and fantasy proneness impact cognitive functioning. Methods: Three groups of participants were included - individuals with DID, individuals with post-traumatic stress disorder (PTSD), and matched healthy controls. Sleep disturbances were measured and compared between the groups along with measures of childhood and adult traumatization, psychoform and somatoform [psychological and somatic] dissociative symptoms, and fantasy proneness. Cognitive capacity was assessed using a working memory task. Results: When controlled for traumatic experiences, sleep disturbances did not predict dissociative symptoms. When controlled for sleep disturbance and fantasy proneness, childhood traumatization did predict dissociative symptoms. Psychoform dissociative symptoms correlated with traumatic experiences more than with fantasy proneness. Working memory performance was similar among the participating groups. Propensity to fantasy did not discriminate individuals with DID and PTSD, and was a weak predictor of dissociative symptoms. Conclusion: Whereas DID and PTSD are associated with sleep disturbances, these features do not statistically predict dissociative symptoms in these disorders when traumatic experiences are taken into account. Fantasy proneness is not excessive in DID and PTSD. Hence, we found no evidence that sleep disturbances, propensity to fantasy and abnormal working memory capacity explain dissociative symptoms in DID and PTSD. In sum, the relationship between sleep and dissociative symptoms disappeared when potentially traumatizing events were controlled for.

Aiding the diagnosis of dissociative identity disorder: pattern recognition study of brain biomarkers

BACKGROUND

A diagnosis of dissociative identity disorder (DID) is controversial and prone to under- and misdiagnosis. From the moment of seeking treatment for symptoms to the time of an accurate diagnosis of DID individuals received an average of four prior other diagnoses and spent 7 years, with reports of up to 12 years, in mental health services.

AIM

To investigate whether data-driven pattern recognition methodologies applied to structural brain images can provide biomarkers to aid DID diagnosis.

METHOD

Structural brain images of 75 participants were included: 32 female individuals with DID and 43 matched healthy controls. Individuals with DID were recruited from psychiatry and psychotherapy out-patient clinics. Probabilistic pattern classifiers were trained to discriminate cohorts based on measures of brain morphology.

RESULTS

The pattern classifiers were able to accurately discriminate between individuals with DID and healthy controls with high sensitivity (72%) and specificity (74%) on the basis of brain structure. These findings provide evidence for a biological basis for distinguishing between DID-affected and healthy individuals.

CONCLUSIONS

We propose a pattern of neuroimaging biomarkers that could be used to inform the identification of individuals with DID from healthy controls at the individual level. This is important and clinically relevant because the DID diagnosis is controversial and individuals with DID are often misdiagnosed. Ultimately, the application of pattern recognition methodologies could prevent unnecessary suffering of individuals with DID because of an earlier accurate diagnosis, which will facilitate faster and targeted interventions.

DECLARATION OF INTEREST

The authors declare no competing financial interests.

Dissociative identity disorder: validity and use in the criminal justice system

This review examines whether the diagnosis of dissociative identity disorder (DID) could be used to support a defence of ‘not guilty by reason of insanity’ (NGRI, or the insanity defence). The problem is that DID has doubtful validity and can easily be malingered. However, the diagnosis is listed in standard psychiatric manuals. If accepted as valid, DID would have problematic forensic implications.

LEARNING OBJECTIVES

After reading this article you will be able to: •

DECLARATION OF INTEREST

None.

Functional reorganization of neural networks involved in emotion regulation following trauma therapy for complex trauma disorders

OBJECTIVES

We investigated whether patients with complex interpersonal trauma engage neural networks that are commonly activated during cognitive reappraisal and responding naturally to affect-laden images. In this naturalistic study, we examined whether trauma treatment not only reduces symptoms but also changes neural networks involved in emotional control.

METHODS

Before and after eight weeks of phase-oriented inpatient trauma treatment, patients (n = 28) with complex posttraumatic stress disorder (cPTSD) and complex dissociative disorders (CDD) performed a cognitive reappraisal task while electroencephalography (EEG) was registered. Patients were measured as a prototypical dissociative part that aims to fulfill daily life goals while avoiding traumatic memories and associated dissociative parts. Matched healthy controls (n = 38) were measured twice as well. We examined task-related functional connectivity and assessed self-reports of clinical symptoms and emotion regulation skills.

RESULTS

Prior to treatment and compared to controls, patients showed hypoconnectivity within neural networks involved in emotional downregulation while reappraising affect-eliciting pictures as well as viewing neutral and affect-eliciting pictures. Following treatment, connectivity became normalized in these networks comprising regions associated with cognitive control and memory. Additionally, patients showed a treatment-related reduction of negative but not of positive dissociative symptoms.

CONCLUSIONS

This is the first study demonstrating that trauma-focused treatment was associated with favorable changes in neural networks involved in emotional control. Emotional overregulation manifesting as negative dissociative symptoms was reduced but not emotional underregulation, manifesting as positive dissociative symptoms.

The long-term effects of single and repeated subanaesthetic ketamine administration on regional cerebral blood flow in healthy dogs measured with 99mTc-HMPAO SPECT

Subanaesthetic ketamine has recently been established as an effective and rapid treatment for major depressive disorder showing antidepressant effects for up to 1 week on average. The use of repeated ketamine infusions has been put forward to augment and to prolong the antidepressant response and increase the remission rates. The underlying neurobiological mechanisms responsible for ketamine's antidepressant effects remain unclear. Nevertheless, it has been shown, both in dogs and humans, that ketamine can alter neuronal perfusion and therefore neuronal function in brain regions involved in psychiatric and behavioural disorders. Consequently, the aim of the current placebo controlled study was to assess the long-term effects on cerebral perfusion of single and repeated subanaesthetic ketamine infusions in dogs. Twelve healthy, laboratory dogs were scanned at six different time points following single and repeated ketamine administration, using Single Photon Emission Computed Tomography with the radiotracer ^99mTc-hexamethylpropylene amine oxime. We hypothesised that repeated infusions could lead to more prolonged perfusion alterations in brain regions critical for behaviour regulation. We found that repeated subanaesthetic ketamine administration did not result in more prolonged cerebral perfusion alterations compared to a single ketamine administration.

Preliminary Evidence of a Missing Self Bias in Face Perception for Individuals with Dissociative Identity Disorder

Failing to recognize one's mirror image can signal an abnormality in one's sense of self. In dissociative identity disorder (DID), individuals often report that their mirror image can feel unfamiliar or distorted. They also experience some of their own thoughts, emotions, and bodily sensations as if they are nonautobiographical and sometimes as if instead, they belong to someone else. To assess these experiences, we designed a novel backwards masking paradigm in which participants were covertly shown their own face, masked by a stranger's face. Participants rated feelings of familiarity associated with the strangers' faces. 21 control participants without trauma-generated dissociation rated masks, which were covertly preceded by their own face, as more familiar compared to masks preceded by a stranger's face. In contrast, across two samples, 28 individuals with DID and similar clinical presentations (DSM-IV Dissociative Disorder Not Otherwise Specified type 1) did not show increased familiarity ratings to their own masked face. However, their familiarity ratings interacted with self-reported identity state integration. Individuals with higher levels of identity state integration had response patterns similar to control participants. These data provide empirical evidence of aberrant self-referential processing in DID/DDNOS and suggest this is restored with identity state integration.

What Mindfulness can learn about Dissociation and what Dissociation can learn from Mindfulness

Mindfulness based psychotherapeutic interventions have shown to be an effective intervention for quite some time now. These intervention, however, have not been that successful with individuals who experience dissociative disorders. There is a very clear disconnect between these two fields. In an attempt to close the gap, reviewing what mindfulness might be from an attachment and human developed lens, one can learn that there is a lot more occurring in a mindful state other than relaxation. There is a level of human development achievement that comes from a regular mindfulness practice that seems to play a role in raising our young and being part of a complex social group. Evidence suggests that the end product of mindfulness is likely deeply connected human relationships and balanced care-giving abilities. In knowing the benefits from a relational perspective of mindfulness those in the dissociative world can utilize adaptations of mindfulness so that their clients can eventually learn to developed mindfulness and, in turn, have the same deeply connected relationship that they often missed. Conversely those in the mindfulness based therapeutic world can learn a lot about dissociation and harmed people by understanding the real difficulties that individuals with dissociative disorders have in experiencing a mindful state. They can learn to understand the need to adapt mindfulness based practices to accommodate individuals who have a system that is phobic of awareness, terrified of being calm and who have no concept of what non-judgement means. Both fields would benefit greatly by knowing more about the other.

Psychotic-Like Symptoms and the Temporal Lobe in Trauma-Related Disorders: Diagnosis, Treatment, and Assessment of Potential Malingering

Objective

To overview the phenomenology, etiology, assessment, and treatment of psychotic-like symptoms in trauma-related disorders focusing on the proposed role of temporal lobe dysfunction.

Method

We describe the literature pertaining to (i) psychotic-like symptoms and temporal lobe dysfunction in trauma-related disorders and (ii) psychological testing profiles in trauma-related disorders. We define trauma-related disorders as borderline personality disorder, post-traumatic stress disorder, and the dissociative disorders. Our search terms were dissociative disorders, temporal lobe, trauma, post-traumatic stress disorder, borderline personality disorder, psychosis, and malingering.

Results

Trauma-related psychotic-like symptoms are common and can differ in phenomenology from primary psychotic symptoms. Hallucinations consist of auditory and nonauditory content that may or may not relate to traumatic content. Child voices are highly suggestive of complex dissociative disorders. Critically, not only do these symptoms resemble those seen in temporal lobe epilepsy, but the temporal lobe is implicated in trauma-related disorders, thus providing a plausible neurobiological explanation. Despite such evidence, these symptoms are frequently considered atypical and misdiagnosed. Indeed, common structured psychological assessment tools categorize these symptoms as possible indicators of invalid testing profiles.

Conclusion

Psychotic-like symptoms are common in trauma-related disorders, may be related to temporal lobe dysfunction, and are frequently misinterpreted. This may lead to ineffective treatment and inappropriate determinations of malingering in the forensic system.

Neurodevelopmental origins of abnormal cortical morphology in dissociative identity disorder

OBJECTIVE

To examine the two constitutes of cortical volume (CV), that is, cortical thickness (CT) and surface area (SA), in individuals with dissociative identity disorder (DID) with the view of gaining important novel insights into the underlying neurobiological mechanisms mediating DID.

METHODS

This study included 32 female patients with DID and 43 matched healthy controls. Between-group differences in CV, thickness, and SA, the degree of spatial overlap between differences in CT and SA, and their relative contribution to differences in regional CV were assessed using a novel spatially unbiased vertex-wise approach. Whole-brain correlation analyses were performed between measures of cortical anatomy and dissociative symptoms and traumatization.

RESULTS

Individuals with DID differed from controls in CV, CT, and SA, with significantly decreased CT in the insula, anterior cingulate, and parietal regions and reduced cortical SA in temporal and orbitofrontal cortices. Abnormalities in CT and SA shared only about 3% of all significantly different cerebral surface locations and involved distinct contributions to the abnormality of CV in DID. Significant negative associations between abnormal brain morphology (SA and CV) and dissociative symptoms and early childhood traumatization (0 and 3 years of age) were found.

CONCLUSIONS

In DID, neuroanatomical areas with decreased CT and SA are in different locations in the brain. As CT and SA have distinct genetic and developmental origins, our findings may indicate that different neurobiological mechanisms and environmental factors impact on cortical morphology in DID, such as early childhood traumatization.

Emotion regulation strategies in trauma-related disorders: pathways linking neurobiology and clinical manifestations

Emotion regulation impairments with traumatic origins have mainly been studied from posttraumatic stress disorder (PTSD) models by studying cases of adult onset and single-incident trauma exposure. The effects of adverse traumatic experiences, however, go beyond the PTSD. Different authors have proposed that PTSD, borderline personality, dissociative, conversive and somatoform disorders constitute a full spectrum of trauma-related conditions. Therefore, a comprehensive review of the neurobiological findings covering this posttraumatic spectrum is needed in order to develop an all-encompassing model for trauma-related disorders with emotion regulation at its center. The present review has sought to link neurobiology findings concerning cortico-limbic function to the field of emotion regulation. In so doing, trauma-related disorders have been placed in a continuum between under- and over-regulation of affect strategies. Under-regulation of affect was predominant in borderline personality disorder, PTSD with re-experiencing symptoms and positive psychoform and somatoform dissociative symptoms. Over-regulation of affect was more prevalent in somatoform disorders and pathologies characterized by negative psychoform and somatoform symptoms. Throughout this continuum, different combinations between under- and over-regulation of affect strategies were also found.

There Is an 'Unconscious,' but It May Well Be Conscious

Depth psychology finds empirical validation today in a variety of observations that suggest the presence of causally effective mental processes outside conscious experience. I submit that this is due to misinterpretation of the observations: the subset of consciousness called “meta-consciousness” in the literature is often mistaken for consciousness proper, thereby artificially creating space for an “unconscious.” The implied hypothesis is that all mental processes may in fact be conscious, the appearance of unconsciousness arising from our dependence on self-reflective introspection for gauging awareness. After re-interpreting the empirical data according to a philosophically rigorous definition of consciousness, I show that two well-known phenomena corroborate this hypothesis: (a) experiences that, despite being conscious, aren’t re-represented during introspection; and (b) dissociated experiences inaccessible to the executive ego. If consciousness is inherent to all mentation, it may be fundamental in nature, as opposed to a product of particular types of brain function.

The extent of dissociation in borderline personality disorder: A meta-analytic review

Several authors have studied dissociation within the borderline personality disorder (BPD) population and postulated 3 dissociative subgroups. Conversely, other authors suggest that dissociation may play a central role in the development of trauma-related disorders and specifically in BPD. Nevertheless, the role of dissociation in BPD seems to be controversial. Our aim is to perform a meta-analytic review of the literature to evaluate the extent of dissociation in BPD compared to other psychopathological disorders to clarify its role in this specific condition. Ten eligible studies resulted in a total of 2,035 subjects. Results show that levels of dissociation are higher in BPD than in other psychiatric disorders in general, although this difference is moderate and the heterogeneity of effect sizes is large. In particular, individuals with BPD seem to show higher levels of dissociation than those with several psychiatric and personality disorders but not dissociative disorders or posttraumatic stress disorder. These findings support the fact that dissociation is not specifically a core feature of BPD and, in addition, sustain the existence of a continuum of severity within the psychiatric population. Nevertheless, the current work has several limitations related to the paucity of studies included, the heterogeneity of control groups, their clear definition, and the statistical robustness of the results. In addition, our conclusions require future research in order to explain the role of different forms of dissociation and their etiological factors among the psychiatric population. Eventually, we invite clinicians and researchers to systematically evaluate dissociation in order to reach a better diagnosis for a more specific treatment indication.

Dissociation and Alterations in Brain Function and Structure: Implications for Borderline Personality Disorder

Dissociation involves disruptions of usually integrated functions of consciousness, perception, memory, identity, and affect (e.g., depersonalization, derealization, numbing, amnesia, and analgesia). While the precise neurobiological underpinnings of dissociation remain elusive, neuroimaging studies in disorders, characterized by high dissociation (e.g., depersonalization/derealization disorder (DDD), dissociative identity disorder (DID), dissociative subtype of posttraumatic stress disorder (D-PTSD)), have provided valuable insight into brain alterations possibly underlying dissociation. Neuroimaging studies in borderline personality disorder (BPD), investigating links between altered brain function/structure and dissociation, are still relatively rare. In this article, we provide an overview of neurobiological models of dissociation, primarily based on research in DDD, DID, and D-PTSD. Based on this background, we review recent neuroimaging studies on associations between dissociation and altered brain function and structure in BPD. These studies are discussed in the context of earlier findings regarding methodological differences and limitations and concerning possible implications for future research and the clinical setting.

Is it Trauma- or Fantasy-based? Comparing dissociative identity disorder, post-traumatic stress disorder, simulators, and controls

OBJECTIVE

The Trauma Model of dissociative identity disorder (DID) posits that DID is etiologically related to chronic neglect and physical and/or sexual abuse in childhood. In contrast, the Fantasy Model posits that DID can be simulated and is mediated by high suggestibility, fantasy proneness, and sociocultural influences. To date, these two models have not been jointly tested in individuals with DID in an empirical manner.

METHOD

This study included matched groups [patients (n = 33) and controls (n = 32)] that were compared on psychological Trauma and Fantasy measures: diagnosed genuine DID (DID-G, n = 17), DID-simulating healthy controls (DID-S, n = 16), individuals with post-traumatic stress disorder (PTSD, n = 16), and healthy controls (HC, n = 16). Additionally, personality-state-dependent measures were obtained for DID-G and DID-S; both neutral personality states (NPS) and trauma-related personality states (TPS) were tested.

CONCLUSION

For Trauma measures, the DID-G group had the highest scores, with TPS higher than NPS, followed by the PTSD, DID-S, and HC groups. The DID-G group was not more fantasy-prone or suggestible and did not generate more false memories. Malingering measures were inconclusive. Evidence consistently supported the Trauma Model of DID and challenges the core hypothesis of the Fantasy Model.

Separating Fact from Fiction: An Empirical Examination of Six Myths About Dissociative Identity Disorder

Dissociative identity disorder (DID) is a complex, posttraumatic, developmental disorder for which we now, after four decades of research, have an authoritative research base, but a number of misconceptualizations and myths about the disorder remain, compromising both patient care and research. This article examines the empirical literature pertaining to recurrently expressed beliefs regarding DID: (1) belief that DID is a fad, (2) belief that DID is primarily diagnosed in North America by DID experts who overdiagnose the disorder, (3) belief that DID is rare, (4) belief that DID is an iatrogenic, rather than trauma-based, disorder, (5) belief that DID is the same entity as borderline personality disorder, and (6) belief that DID treatment is harmful to patients. The absence of research to substantiate these beliefs, as well as the existence of a body of research that refutes them, confirms their mythical status. Clinicians who accept these myths as facts are unlikely to carefully assess for dissociation. Accurate diagnoses are critical for appropriate treatment planning. If DID is not targeted in treatment, it does not appear to resolve. The myths we have highlighted may also impede research about DID. The cost of ignorance about DID is high not only for individual patients but for the whole support system in which they reside. Empirically derived knowledge about DID has replaced outdated myths. Vigorous dissemination of the knowledge base about this complex disorder is warranted.

The Psychobiology of Authentic and Simulated Dissociative Personality States: The Full Monty

The etiology of dissociative identity disorder (DID) remains a topic of debate. Proponents of the fantasy model and the trauma model of DID have both called for more empirical research. To this end, the current study presents new and extended data analyses of a previously published H2O positron emission tomography imaging study. This study included 29 subjects: 11 patients with DID and 10 high- and 8 low-fantasy-prone DID-simulating mentally healthy control subjects. All subjects underwent an autobiographical memory script-driven (neutral and trauma related) imagery paradigm in 2 (simulated) dissociative personality states (neutral and trauma related). Psychobiological and psychophysiological data were obtained. Results of the new post-hoc tests on the psychophysiological responses support the trauma model. New results of the brain imaging data did not support the fantasy model. This study extends previously published results by offering important new supporting data for the trauma model of DID.

Similar cortical but not subcortical gray matter abnormalities in women with posttraumatic stress disorder with versus without dissociative identity disorder

Neuroanatomical evidence on the relationship between posttraumatic stress disorder (PTSD) and dissociative disorders is still lacking. We acquired brain structural magnetic resonance imaging (MRI) scans from 17 patients with dissociative identity disorder (DID) and co-morbid PTSD (DID-PTSD) and 16 patients with PTSD but without DID (PTSD-only), and 32 healthy controls (HC), and compared their whole-brain cortical and subcortical gray matter (GM) morphological measurements. Associations between GM measurements and severity of dissociative and depersonalization/derealization symptoms or lifetime traumatizing events were evaluated in the patient groups. DID-PTSD and PTSD-only patients, compared with HC, had similarly smaller cortical GM volumes of the whole brain and of frontal, temporal and insular cortices. DID-PTSD patients additionally showed smaller hippocampal and larger pallidum volumes relative to HC, and larger putamen and pallidum volumes relative to PTSD-only. Severity of lifetime traumatizing events and volume of the hippocampus were negatively correlated. Severity of dissociative and depersonalization/derealization symptoms correlated positively with volume of the putamen and pallidum, and negatively with volume of the inferior parietal cortex. Shared abnormal brain structures in DID-PTSD and PTSD-only, small hippocampal volume in DID-PTSD, more severe lifetime traumatizing events in DID-PTSD compared with PTSD-only, and negative correlations between lifetime traumatizing events and hippocampal volume suggest a trauma-related etiology for DID. Our results provide neurobiological evidence for the side-by-side nosological classification of PTSD and DID in the DSM-5.