A. A. T. Simone Reinders

Background: Dissociative identity disorder (DID) manifests with distinct trauma-avoidant and trauma-related identity states. Overtly conscious trauma-related knowledge processing is identity state-dependent. Previous research on covertly subconscious knowledge processing in DID lacks subject-specific trauma-related stimuli. Aims: Our controlled functional magnetic resonance imaging (fMRI) study explored neural and behavioural differences of overt and covert knowledge processing of individualised self-relevant words in DID. Method: Behavioural data were gathered while 56 participants underwent task-based fMRI: 14 with DID, 14 DID simulators and a paired control group of 14 healthy controls and 14 participants with post-traumatic stress disorder. Individuals with DID and simulators participated in a trauma-avoidant and a trauma-related identity state. Reaction times and brain activation following overtly and covertly presented individualised words were statistically analysed. Results: Behavioural analyses showed a main effect of consciousness ( P < 0.001). Post hoc between-group pairwise comparisons revealed slower reaction times for individuals with DID compared with simulating ( P < 0.05) and paired controls ( P < 0.05). Neural data analyses showed increased brain activation in frontal and parietal regions within the diagnosed DID group, especially during overt processing. Between-group comparisons mostly showed less pronounced activation in frontal, occipital and temporal areas. Conclusions: The present study showed increased cognitive control during overt self-relevant knowledge processing in the trauma-avoidant identity state of DID, in line with previous research. The slower reaction times and increased frontoparietal activation shown in individuals with diagnosed DID, as compared with both control groups, support the notion of cognitive avoidance of trauma-related information in DID and further reinforce the authenticity of DID experiences.

Objective: Dissociative states, characterised by discontinuities in awareness and perception, occur in a diverse array of psychiatric disorders and contexts. Dissociative states have been experimentally modelled in the laboratory through various induction methods but relatively little is known about the efficacy and comparability of different experimental methods. Methods: This meta-analysis quantified dissociative states, as indexed by a standardised instrument ( Clinician Administered Dissociative States Scale ), at baseline in varied diagnostic categories and in response to different experimental induction methods (psychological techniques and pharmacological agents) in both clinical and non-clinical samples. Primary outcomes were state dissociation effect sizes (Hedges’s g ) (PROSPERO registration CRD42022384886). Results: 2,214 papers were screened, yielding 123 eligible articles and 155 effect sizes comprising 6,692 individuals. High levels of baseline state dissociation were observed in multiple diagnostic categories relative to controls, with the largest effects found in the dissociative and complex subtypes of post-traumatic stress disorder (PTSD-DC). In controlled experiments, induced state dissociation was most pronounced in response to mirror-gazing and multiple pharmacological agents with effects exceeding baseline state dissociation in PTSD-DC in ketamine and cannabis. The effect sizes were characterised by pronounced heterogeneity but were not reliably associated with methodological features of the original studies. Conclusions: Elevated state dissociation is present in multiple diagnostic categories and comparable or higher levels can be reliably induced in controlled experiments using psychological techniques and pharmacological agents. These results demonstrate the efficacy of several methods for experimentally modelling dissociation and have implications for measuring adverse events and predicting outcomes in clinical interventions involving pharmacological agents.

This study aimed to provide a preliminary assessment of objective and subjective neurocognitive functioning in individuals with functional motor symptoms (FMS) and/or functional seizures (FS). We tested the hypotheses that the FMS/FS group would display poorer objective attentional and executive functioning, altered social cognition, and reduced metacognitive accuracy. Individuals with FMS/FS (n = 16) and healthy controls (HCs, n = 17) completed an abbreviated CANTAB battery, and measures of intellectual functioning, subjective cognitive complaints, performance validity, and comorbid symptoms. Subjective performance ratings were obtained to assess local metacognitive accuracy. The groups were comparable in age (p = 0.45), sex (p = 0.62), IQ (p = 0.57), and performance validity (p-values = 0.10-0.91). We observed no impairment on any CANTAB test in this FMS/FS sample compared to HCs, although the FMS/FS group displayed shorter reaction times on the Emotional Bias task (anger) (p = 0.01, np2 = 0.20). The groups did not differ in subjective performance ratings (p-values 0.15). Whilst CANTAB attentional set-shifting performance (total trials/errors) correlated with subjective performance ratings in HCs (p-valuess = -0.85), these correlations were non-significant in the FMS/FS sample (p-values = 0.10-0.13, r_s-values = -0.46-0.50). The FMS/FS group reported more daily cognitive complaints than HCs (p = 0.006, g = 0.92), which were associated with subjective performance ratings on CANTAB sustained attention (p = 0.001, r_s = -0.74) and working memory tests (p < 0.001, r_s = -0.75), and with depression (p = 0.003, r_s = 0.70), and somatoform (p = 0.003, r_s = 0.70) and psychological dissociation (p-valuess-values = 0.67-0.85). These results suggest a discordance between objective and subjective neurocognitive functioning in this FMS/FS sample, reflecting intact test performance alongside poorer subjective cognitive functioning. Further investigation of neurocognitive functioning in FND subgroups is necessary.

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.

Background: Differences in affective processing have previously been shown in functional neurological disorder (FND); however, the mechanistic relevance is uncertain. We tested the hypotheses that highly arousing affective stimulation would result in elevated subjective functional neurological symptoms (FNS), and this would be associated with elevated autonomic reactivity. The possible influence of cognitive detachment was also explored. Methods: Individuals diagnosed with FND (motor symptoms/seizures; n=14) and healthy controls (HCs; n=14) viewed Positive, Negative, and Neutral images in blocks, whilst passively observing the stimuli (“Watch”) or detaching themselves (“Distance”). The FND group rated their primary FNS, and all participants rated subjective physical (arousal, pain, fatigue) and psychological states (positive/negative affect, dissociation), immediately after each block. Skin conductance (SC) and heartrate (HR) were monitored continuously. Results: FNS ratings were higher after Negative compared to Positive and Neutral blocks in the FND group (p=0.002, η _p ² =0.386); however, this effect was diminished in the Distance condition relative to the Watch condition (p=0.018, η _p ² =0.267). SC and/or HR correlated with FNS ratings in the Negative-Watch and Neutral-Distance conditions (r-values: 0.527-0.672, p-values: 0.035-0.006). The groups did not differ in subjective affect or perceived arousal (p-values: 0.541-0.919, η _p ² : <0.001-0.015). Conclusions: Emotionally significant events may exert an influence on FNS which is related to autonomic activation rather than altered subjective affect or perceived arousal. This influence may be modulated by cognitive detachment. Further work is needed to determine the relevance and neural bases of these processes in specific FND phenotypes.

Summary: Dissociative symptoms present transdiagnostically and are related to poor clinical outcome. Research into the biological correlates of dissociation remains limited. This editorial summarises and discusses papers from this themed series of BJPsych Open that contribute to unravelling the biological correlates of dissociative symptomatology with the aim of improving treatment and treatment outcome.

The elusive search for a biomarker of dissociative amnesia: an overstated response to understated findings?-CORRIGENDUM.