Dissociation In Posttraumatic Stress Disorder Research Articles

Disentangling the Link Between Mindfulness and Dissociation in PTSD: The Mediating Role of Attention and Emotional Acceptance

ABSTRACT Introduction A number of studies have investigated the relationship between mindfulness and dissociation and suggested that mindfulness-based interventions could be effective in the treatment of dissociative symptoms. A recent study in healthy volunteers found that attention and emotional acceptance mediates this relationship. However, no study has yet been performed among a clinical sample to assess this association. Method We recruited 90 patients (76 women) suffering from Posttraumatic Stress Disorder (PTSD). They completed self-report questionnaires to measure PTSD, dissociation, emotion regulation difficulties, childhood trauma, mindfulness abilities and cognitive abilities. Results We found that mindfulness abilities, emotional difficulties, dissociation and attention-concentration were all related to each other. Using a step-by-step approach and bootstrapping techniques, we found a significant indirect effect of mindfulness abilities on dissociation through non-acceptance (confidence interval 95%=-.14 to −.01) and attentional difficulties (confidence interval 95%=-.23 to −.05). Conclusion Patients with higher levels of dissociative symptoms have less capacity for mindfulness. Our results support Bishop et al.’s model proposing that attention and emotional acceptance are the two active components of mindfulness. To extend our findings, clinical trials are required to evaluate a causal relationship and the effectiveness of mindfulness-based interventions for patients suffering from dissociation.

Imaging dissociation in post-traumatic stress disorder.

Symptom provocation paradigms have been successfully developed to identify the neural correlates associated with post-traumatic stress disorder (PTSD) symptoms, especially dissociative behaviours, but have critical limitations. Transiently stimulating the sympathetic nervous system and/or the hypothalamic-pituitary-adrenal (HPA) axis can enhance the stress response to symptom provocation and would help identify targets for personalised interventions.

Gender Differences in the Symptomatology of Posttraumatic Stress Disorder among Syrian Refugees Settled in a Camp in Turkey.

This study firstly described gender differences in traumatic experiences and the symptomatology and posttraumatic stress disorder (PTSD), among Syrian refugees settled in a camp in Turkey. Secondly, we aimed to discuss the reasons for gender differences, by comparing with the studies conducted on these Syrian refugees of the same culture who are the victims of the same war in their new settlement where they had been forced to migrate. This cross-sectional study was carried out on 352 refugees, randomly selected from a single settlement. The diagnosis of PTSD was performed using face-to-face psychiatric interviews according to the DSM-IV-TR criteria. The Stressful Life Events Screening Questionnaire and a sociodemographic history form were administered to all participants. We compared our results with other PTSD studies on Syrian Refugees. Men were exposed to traumatic events 1.29 times more frequently than women. However, the prevalence of PTSD was significantly higher in women (44.1%) than in men (18.1%), with a prevalence of 30.7% in the overall sample. While symptoms of intrusion and avoidance/numbing were more prevalent in women with PTSD, there was no difference in symptoms of hypervigilance between genders. However, women reported a higher prevalence of fear response to traumatic events. Female refugees may be more prone than men to develop PTSD, although both genders shared the same traumatic environment in the early post-traumatic periods. The higher frequency of intrusion and avoidance/numbing may originate from an increased tendency of anxiety structural dissociation among women, alongside possibly higher peritraumatic dissociation, which may be also boosted by the higher ongoing perception of threat among female refugees. The possible role of peritraumatic and ongoing dissociation in PTSD should be taken into consideration for further research, particularly among populations under ongoing threat.

Proactive Interference in Posttraumatic Stress Disorder.

Deficits in working memory (WM) have a role in maintaining posttraumatic stress disorder (PTSD) symptoms, including intrusions, which are a hallmark of PTSD symptomatology. As intrusions are distressing and uncontrollable, it is important to investigate whether PTSD is associated with altered control of proactive interference in WM. Moreover, it is important to consider both verbal and visual WM, as previous research has demonstrated a visual versus verbal dissociation in PTSD. Although previous studies have explored proactive interference in visual and verbal stimuli using a recent probe task, the stimuli used thus far have been non-trauma-related. Therefore, we aimed to investigate proactive interference in PTSD using trauma-related verbal and visual stimuli. Road traffic accident (RTA) survivors with (n = 60) and without PTSD (n = 30) completed a recent probe task to assess proactive interference of visual and verbal trauma-related material. Participants with PTSD displayed significantly more proactive interference than trauma-exposed controls for visual, ηp 2 = .40, and verbal material, ηp 2 = .10, indicating that proactive interference is significantly impaired in PTSD. This demonstrates that further research is warranted and highlights the possibility of considering proactive interference of trauma-related stimuli in therapeutic approaches.

Dissociative identity disorder: a developmental perspective

SUMMARYDissociation is a common and often overlooked symptom in traumatised children. Although there is a lack of a scientific consensus as to the nature of dissociation and very limited research about dissociative identity disorder (DID) in children, the authors have seen children given this diagnosis recently referred to their clinic and are concerned about this practice and the parenting approaches that have ensued. The diagnosis of DID in children may be rare or of doubtful validity, but repeated traumatic experiences of an interpersonal nature can have a profound effect on a child's identity, memory and self-organisation. Furthermore, abuse and neglect can increase the risk of dissociative symptoms. This brief article considers dissociation in post-traumatic stress disorder, then outlines developmental factors hypothesised to be associated with dissociation in childhood and early adulthood. It warns that clinicians should keep an open mind about how dissociation may manifest transdiagnostically, and concludes with recommendations for further research.

The dissociative subtype of posttraumatic stress disorder is associated with subcortical white matter network alterations

Posttraumatic stress disorder (PTSD) is characterized by intrusions, avoidance, and hyperarousal while patients of the dissociative subtype (PTSD-D) experience additional dissociative symptoms. A neurobiological model proposes hyper-inhibition of limbic structures mediated by prefrontal cortices to underlie dissociation in PTSD. Here, we tested whether functional alterations in fronto-limbic circuits are underpinned by white matter network abnormalities on a network level. 23 women with PTSD-D and 19 women with classic PTSD participated. We employed deterministic diffusion tractography and graph theoretical analyses. Mean fractional anisotropy (FA) was chosen as a network weight and group differences assessed using network-based statistics. No significant white matter network alterations comprising both frontal and limbic structures in PTSD-D relative to classic PTSD were found. A subsequent whole brain exploratory analysis revealed relative FA alterations in PTSD-D in two subcortical networks, comprising connections between the left amygdala, hippocampus, and thalamus as well as links between the left ventral diencephalon, putamen, and pallidum, respectively. Dissociative symptom severity in the PTSD-D group correlated with FA values within both networks. Our findings suggest fronto-limbic inhibition in PTSD-D may present a dynamic neural process, which is not hard-wired via white matter tracts. Our exploratory results point towards altered fiber tract communication in a limbic-thalamic circuit, which may underlie (a) an initial strong emotional reaction to trauma reminders before conscious regulatory processes are enabled and (b) deficits in early sensory processing. In addition, aberrant structural connectivity in low-level motor regions may present neural correlates for dissociation as a passive threat-response.

Do Patients Underestimate Their Symptoms in Hindsight? An Ambulatory Assessment Study on the Frequency of Dissociation in Posttraumatic Stress Disorder

Assessing symptom frequencies is a core feature of psychological diagnostics and any evaluation of the effectiveness of a therapeutic approach is based on these. However, heuristic strategies are employed when estimating the frequency of past events, which can lead to recall biases. While the few studies published to date indicate that patients suffering from posttraumatic stress disorder tend to underreport dissociative symptoms, there is also some evidence for the tendency to overreport dissociative symptoms. To gain insights into absolute frequencies of dissociative symptoms and retrospective reporting styles we used ambulatory assessment in 42 participants with PTSD symptoms. Participants logged their symptoms via smartphone over 2 weeks and then estimated them again retrospectively for this entire period. In comparison to the daily logs, more participants tended to retrospectively underestimate experienced symptoms in their frequency for almost all items. The results reported in this sample thus argue for an underreporting style instead of overreporting of dissociative symptoms.

The Threatful Self: Midbrain Functional Connectivity to Cortical Midline and Parietal Regions During Subliminal Trauma-Related Processing in PTSD

Background The innate alarm system consists of a subcortical network of interconnected midbrain, lower brainstem, and thalamic nuclei, which together mediate the detection of evolutionarily-relevant stimuli. The periaqueductal gray is a midbrain structure innervated by the innate alarm system that coordinates the expression of defensive states following threat detection. In participants with post-traumatic stress disorder, the periaqueductal gray displays overactivation during the subliminal presentation of trauma-related stimuli as well as altered resting-state functional connectivity. Aberrant functional connectivity is also reported in post-traumatic stress disorder for the default-mode network, a large-scale brain network recruited during self-referential processing and autobiographical memory. Here, research lacks investigation on the extent to which functional interactions are displayed between the midbrain and the large-scale cortical networks in post-traumatic stress disorder. Methods Using a subliminal threat presentation paradigm, we investigated psycho-physiological interactions during functional neuroimaging in participants with post-traumatic stress disorder (n = 26) and healthy control subjects (n = 20). Functional connectivity of the periaqueductal gray was investigated across the whole-brain of each participant during subliminal exposure to trauma-related and neutral word stimuli. Results As compared to controls during subliminal threat presentation, the post-traumatic stress disorder group showed significantly greater periaqueductal gray functional connectivity with regions of the default-mode network (i.e., angular gyrus, precuneus, superior frontal gyrus). Moreover, multiple regression analyses revealed that the functional connectivity between the periaqueductal gray and the regions of the default-mode network correlated positively to symptoms of avoidance and state dissociation in post-traumatic stress disorder. Conclusion Given that the periaqueductal gray engages the expression of defensive states, stronger midbrain functional coupling with the default-mode network may have clinical implications to self-referential and trauma-related processing in participants with post-traumatic stress disorder.

Dissociation between working memory performance and proactive interference control in post-traumatic stress disorder

Deficits in working memory (WM) and cognitive control processes have been reported in post-traumatic stress disorder (PTSD), in addition to clinical symptoms such as hypervigilance, re-experiencing, and avoidance of trauma reminders. Given the uncontrollable nature of intrusive memories, an important question is whether PTSD is associated with altered control of interference in WM. Some studies also suggest that episodic memory shows a material-specific dissociation in PTSD, with greater impairments in verbal memory and relative sparing of nonverbal memory. It is unclear whether this dissociation applies to WM, as no studies have used identical task parameters across material. Here we tested 29 combat Veterans with PTSD and 29 age-matched control Veterans on a recent probes WM task with words and visual patterns in separate blocks. Participants studied four-item sets, followed by a probe stimulus that had been presented in the previous set (recent probe) or not (nonrecent probe). Participants with PTSD made more errors than controls, and this decrement was similar for verbal and visual stimuli. Proactive interference from items recently presented, but no longer relevant, was not significantly different in the PTSD group and showed no relationship to re-experiencing symptom severity. These results demonstrate that PTSD is not reliably associated with increased intrusions of irrelevant representations into WM when non-emotional stimuli are used. Future studies that use trauma-related material may provide insight into the flashbacks and intrusive thoughts that plague those with PTSD.

Survivor–spouse dissociation and posttraumatic stress disorder: Personal and dyad relationships

ABSTRACTThis study examined the relationships between dissociation and posttraumatic stress disorder (PTSD) symptoms among injured survivors of terror attacks and their spouses (N = 210), specifically exploring survivor–spouse dyadic associations. Structural equation modeling and the actor–partner interdependence model were used to test the bidirectional dyadic association of both the survivors’ and the spouses’ dissociation with PTSD symptoms. The results demonstrated a positive association both between the survivors’ trait dissociation and PTSD symptoms and between the spouses’ trait dissociation and their PTSD symptoms. However, no significant associations were found at the bidirectional level. Taken together, our findings shed new light on the role of trait dissociation in PTSD. Although trait dissociation is associated with higher PTSD symptoms for both survivors and their spouses, its role may be limited in the bidirectional partner context. Theoretical and clinical implications of the findings are discussed.

Dimensions and Dissociation in PTSD in the DSM-5: Towards Eight Core Symptoms

The article reviews the literature on the dimensional (factor) structure of posttraumatic stress disorder (PTSD) as presented in the DSM-5 (Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition; American Psychiatric Association, 2013). The DSM-5 PTSD diagnostic category contains 20 symptoms split into four factors. Also, the article considers the literature on the dissociative subtype, which is found in a minority of PTSD cases. The literature shows that the DSM (Diagnostic and Statistical Manual of Mental Disorders) over the years has moved from a three-dimensional structure in prior DSMs to one with four dimensions in the DSM-5. However, the research reviewed queries whether the DSM-5’s four dimensions are consistent with the empirical literature; in this regard, models with five and six dimensions were the first to suggest alternatives. Moreover, in the literature, the DSM-5 symptoms appear to group into as many as seven dimensions, which are as follows: re-experiencing, avoidance, negative affect, anhedonia, externalizing behavior, anxious arousal, and dysphoric arousal (Armour et al., Journal of Psychiatric Research 61: 106–113, 2015; Wang et al., Journal of Anxiety Disorders 31: 90–97, 2015). In particular, the two DSM-5 dimensions of negative alterations in cognitions and mood and alterations in arousal and reactivity appear to be subdivided into five dimensions. Generally, the 20 PTSD symptoms and their suggested factors that are found in the literature could prove unwieldy to clinicians. Moreover, they allow for much heterogeneity in symptom expression among PTSD cases. In response, the article presents a model of PTSD based on the seven-factor dimensional structure emerging in the literature, as well as another factor associated with the dissociation subtype, but with one core or primary symptom specified for each of the dimensions. The article considers forensic implications of the newer models on PTSD’s dimensional structure.

Traumatic dissociation as a predictor of posttraumatic stress disorder in South African female rape survivors.

Women survivors of rape are at an increased risk for posttraumatic stress disorder (PTSD). Traumatic dissociation has been identified as a precursor of PTSD. This study assessed the predictive potential of traumatic dissociation in PTSD and depression development.The study followed a longitudinal, prospective design. Ninety-seven female rape survivors were recruited from 2 clinics in Cape Town, South Africa. Clinical interviews and symptom status assessments of the participants were completed to measure dissociation, childhood traumas, resilience, depression, and PTSD.Traumatic dissociation was a significant predictor of PTSD and depression. The linear combination of prior dissociation, current dissociation, and resilience significantly explained 20.7% of the variance in PTSD. Dissociation mediated the relationship between resilience and PTSD.As traumatic dissociation significantly predicts PTSD, its early identification and management may reduce the risk of developing PTSD. Interventions focused on promoting resilience may also be successful in reducing the risk of dissociation following rape.

Dysregulation in cortical reactivity to emotional faces in PTSD patients with high dissociation symptoms

BackgroundPredominant dissociation in posttraumatic stress disorder (PTSD) is characterized by restricted affective responses to positive stimuli. To date, no studies have examined neural responses to a range of emotional expressions in PTSD with high dissociative symptoms.ObjectiveThis study tested the hypothesis that PTSD patients with high dissociative symptoms will display increased event-related potential (ERP) amplitudes in early components (N1, P1) to threatening faces (angry, fearful), and reduced later ERP amplitudes (Vertex Positive Potential (VPP), P3) to happy faces compared to PTSD patients with low dissociative symptoms.MethodsThirty-nine civilians with PTSD were classified as high dissociative (n=16) or low dissociative (n=23) according to their responses on the Clinician Administered Dissociative States Scale. ERPs were recorded, whilst participants viewed emotional (happy, angry, fear) and neutral facial expressions in a passive viewing task.ResultsHigh dissociative PTSD patients displayed significantly increased N120 amplitude to the majority of facial expressions (neutral, happy, and angry) compared to low dissociative PTSD patients under conscious and preconscious conditions. The high dissociative PTSD group had significantly reduced VPP amplitude to happy faces in the conscious condition.ConclusionHigh dissociative PTSD patients displayed increased early (preconscious) cortical responses to emotional stimuli, and specific reductions to happy facial expressions in later (conscious), face-specific components compared to low dissociative PTSD patients. Dissociation in PTSD may act to increase initial pre-attentive processing of affective stimuli, and specifically reduce cortical reactivity to happy faces when consciously processing these stimuli.

Dissociation in Posttraumatic Stress Disorder: Evidence from the World Mental Health Surveys

Although the proposal for a dissociative subtype of posttraumatic stress disorder (PTSD) in DSM-5 is supported by considerable clinical and neurobiological evidence, this evidence comes mostly from referred samples in Western countries. Cross-national population epidemiologic surveys were analyzed to evaluate generalizability of the subtype in more diverse samples. Interviews were administered to 25,018 respondents in 16 countries in the World Health Organization World Mental Health Surveys. The Composite International Diagnostic Interview was used to assess 12-month DSM-IV PTSD and other common DSM-IV disorders. Items from a checklist of past-month nonspecific psychological distress were used to assess dissociative symptoms of depersonalization and derealization. Differences between PTSD with and without these dissociative symptoms were examined across a variety of domains, including index trauma characteristics, prior trauma history, childhood adversity, sociodemographic characteristics, psychiatric comorbidity, functional impairment, and treatment seeking. Dissociative symptoms were present in 14.4% of respondents with 12-month DSM-IV/Composite International Diagnostic Interview PTSD and did not differ between high and low/middle income countries. Symptoms of dissociation in PTSD were associated with high counts of re-experiencing symptoms and net of these symptom counts with male sex, childhood onset of PTSD, high exposure to prior (to the onset of PTSD) traumatic events and childhood adversities, prior histories of separation anxiety disorder and specific phobia, severe role impairment, and suicidality. These results provide community epidemiologic data documenting the value of the dissociative subtype in distinguishing a meaningful proportion of severe and impairing cases of PTSD that have distinct correlates across a diverse set of countries.

Dissociation in posttraumatic stress disorder part I: Definitions and review of research.

Since Janet wrote about dissociation in the early 1900s, the relationship between traumatic stress and dissociation has been discussed and debated in the fields of psychology and psychiatry. In the last 25 years, research has been conducted that allows empirical examination of this relationship and the question of how dissociative symptoms are related to posttraumatic stress disorder (PTSD). After defining the types of dissociative experiences that are considered most relevant to PTSD, we present a comprehensive and systematic review of research addressing the relationship between dissociation and traumatic stress; the rise in dissociation after traumatic stress and its subsequent decline over time; the relationship between dissociation and symptoms of PTSD in nonclinical, clinical, and PTSD samples; the conditional probability of high PTSD symptoms when dissociation level is high; the relationships among dissociation and re-experiencing, avoidance, and hyperarousal symptoms of PTSD; and biological studies of dissociation in PTSD.

Investigating Cognitive Pathways to Psychopathology: Predicting Depression and Posttraumatic Stress Disorder From Early Responses After Assault.

Depression and posttraumatic stress disorder (PTSD) are common after trauma, but it remains unclear what factors determine which disorder a trauma survivor will develop. A prospective longitudinal study of 222 assault survivors assessed candidate predictors derived from cognitive models of depression and PTSD at 2 weeks posttrauma (N = 222), and depression and PTSD symptom severities (N = 183, 82%) and diagnoses at 6 months (N = 205, 92%). Structural equation modeling showed that the depression and PTSD models predicted both depression and PTSD symptom severity, but that the disorder-specific models predicted the respective outcome best (43% for depression, 59% for PTSD symptom severity). Maintaining cognitive variables (hopelessness and self-devaluative thoughts in depression; cognitive responses to intrusive memories and persistent dissociation in PTSD) showed the clearest specific relationships with outcome. Model-derived variables predicted depression and PTSD diagnoses at 6 months over and above what could be predicted from initial diagnoses. Results support the role of cognitive factors in the development of depression and PTSD after trauma, and provide preliminary evidence for some specificity in maintaining cognitive mechanisms.

Neuropsychological Characteristics of Highly Dissociative Healthy Individuals

ABSTRACT Objective: Dissociative disorders are characterized by disturbances in several neuropsychological domains, especially attention, memory, and consciousness. As a tendency to dissociate can also be observed in healthy individuals, and may be a risk factor for the development of dissociative disorders and posttraumatic stress disorder (PTSD), we were interested in the neuropsychological characteristics of these participants. Method: We examined attention, memory, and executive control functions in 17 high and 17 low dissociators without any psychiatric or neurological disorder and without prior experiences of trauma. Results: High dissociators showed relative performance deficiencies in tasks of memory for associative, context-dependent verbal material, visuospatial working memory, and executive control functions in terms of a heightened perseveration tendency and false positive errors. Conclusion: These cognitive deficits are consistent with models of dissociative disorders and dissociation in PTSD assuming a hippocampal and prefrontal dysfunction as a core factor. Mild cognitive impairments in otherwise healthy high dissociators may constitute a risk factor for the development of later PTSD or dissociative disorders.

Neural correlates of reexperiencing, avoidance, and dissociation in PTSD: Symptom dimensions and emotion dysregulation in responses to script‐driven trauma imagery

Research suggests that responses to script-driven trauma imagery in posttraumatic stress disorder (PTSD) include reexperiencing and dissociative symptom subtypes. This functional magnetic resonance imaging (fMRI) study employed a dimensional approach to characterizing script-driven imagery responses, using the Responses to Script-Driven Imagery Scale and correlational analyses of relationships between severity of state posttraumatic symptoms and neural activation. As predicted, state reexperiencing severity was associated positively with right anterior insula activity and negatively with right rostral anterior cingulate cortex (rACC). Avoidance correlated negatively with rACC and subcallosal anterior cingulate activity. In addition, as predicted, dissociation correlated positively with activity in the left medial prefrontal and right superior temporal cortices, and negatively with the left superior temporal cortex. Theoretical and clinical implications are discussed, particularly with respect to an emotion-dysregulation account of PTSD.

More Evidence for the Role of Persistent Dissociation in PTSD

Back to table of contents Previous article Next article Letters to the EditorFull AccessMore Evidence for the Role of Persistent Dissociation in PTSDANKE EHLERS Ph.D.,ANKE EHLERS Ph.D.Search for more papers by this author,Published Online:1 Jun 2006AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InEmail To the Editor: The report by Briere and colleagues (1) highlights the importance of persistent dissociation in the etiology of posttraumatic stress disorder (PTSD). On the basis of two cross-sectional studies, the authors conclude that “the primary risk for PTSD is less whether one dissociates during (or soon after) a traumatic event than whether such dissociation persists over time” (p. 2299). We agree with the authors’ conclusions. It is of interest to note that our article published in 2002 in the British Journal of Psychiatry(2) reported two prospective longitudinal studies of motor vehicle accident survivors and came to a remarkably similar conclusion: “Persistent dissociation and rumination 4 weeks after trauma are more useful in identifying those patients who are likely to develop chronic PTSD than initial reactions.” Participants were assessed very soon after the accident and followed for 6 months. Persistent dissociation at 4 weeks was a better predictor of chronic PTSD at 6 months than peritraumatic dissociation measured in the immediate aftermath of the trauma. Another prospective longitudinal study of assault survivors published in 2003 in the Journal of Consulting and Clinical Psychology(3) showed that persistent dissociation predicted an additional 8% variance of PTSD severity at 6 months over and above what could be predicted from trauma severity and cognitive processing measures, including peritraumatic dissociation. These findings from prospective longitudinal studies complement the cross-sectional results of Briere and colleagues and support their conclusion. The role of persistent dissociation as a maintaining factor is also highlighted in recent psychological models of chronic PTSD (eg., 4 ). London, U.K.

More Evidence for the Role of Persistent Dissociation in PTSD

Back to table of contents Previous article Next article Letters to the EditorFull AccessMore Evidence for the Role of Persistent Dissociation in PTSDANKE EHLERS Ph.D.,ANKE EHLERS Ph.D.Search for more papers by this author,Published Online:1 Jun 2006AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InEmail To the Editor: The report by Briere and colleagues (1) highlights the importance of persistent dissociation in the etiology of posttraumatic stress disorder (PTSD). On the basis of two cross-sectional studies, the authors conclude that “the primary risk for PTSD is less whether one dissociates during (or soon after) a traumatic event than whether such dissociation persists over time” (p. 2299). We agree with the authors’ conclusions. It is of interest to note that our article published in 2002 in the British Journal of Psychiatry(2) reported two prospective longitudinal studies of motor vehicle accident survivors and came to a remarkably similar conclusion: “Persistent dissociation and rumination 4 weeks after trauma are more useful in identifying those patients who are likely to develop chronic PTSD than initial reactions.” Participants were assessed very soon after the accident and followed for 6 months. Persistent dissociation at 4 weeks was a better predictor of chronic PTSD at 6 months than peritraumatic dissociation measured in the immediate aftermath of the trauma. Another prospective longitudinal study of assault survivors published in 2003 in the Journal of Consulting and Clinical Psychology(3) showed that persistent dissociation predicted an additional 8% variance of PTSD severity at 6 months over and above what could be predicted from trauma severity and cognitive processing measures, including peritraumatic dissociation. These findings from prospective longitudinal studies complement the cross-sectional results of Briere and colleagues and support their conclusion. The role of persistent dissociation as a maintaining factor is also highlighted in recent psychological models of chronic PTSD (eg., 4 ). London, U.K.