Paul Brown, Onno van der Hart (1998)
Memories of sexual abuse: Janet's critique of Freud, a balanced approach.
Psychol Rep. 1998 Jun;82(3 Pt 1):1027-43.

Abstract: Since the late nineteenth century explanations of sexual trauma have invoked unconscious mental mechanisms of forgetting. Memories have been seen as submerged only to be therapeutically recovered. Explanations and related therapies have tended to be either hotly advocated or decried, not the least were those of Janet and Freud. Once again there is a vigorous debate surrounding the status of recovered memories. This paper was undertaken to contribute to reasoned and balanced dialogue by exploring an historical dimension. There is a renaissance of interest in the oeuvre of Janet. In this article Janetian sources are examined in which he criticised Freud's views on sexual trauma and elaborated his own position, a position which is yet significant today.

Madelon L. Peters, Seger A. Uyterlinde, John Consemulder and Onno van der Hart (1998)
Apparent amnesia on experimental memory tests in dissociative identity disorder: an exploratory study.
Conscious Cogn. 1998 Mar;7(1):27-41.
doi:10.1006/ccog.1997.0323

Abstract: Dissociative identity disorder (DID; called multiple personality disorder in DSMIII-R) is a psychiatric condition in which two or more identity states recurrently take control of the person's behavior. A characteristic feature of DID is the occurrence of apparently severe amnestic symptoms. This paper is concerned with experimental research of memory function in DID and focuses on between-identity transfer of newly learned neutral material. Previous studies on this subject are reviewed and a pilot study with four subjects is described. This study is specifically concerned with the question whether self-reported asymmetries in between-identity transfer can be replicated on experimental memory tests. A secondary aim was to examine whether, in the absence of explicit transfer, implicit transfer of information would occur. The results showed that the apparent amnestic asymmetry for explicit information was substantiated in the laboratory, although at least some leakage was present between the apparently amnestic identities. No evidence was found for better performance on implicit than on explicit memory tests in the apparently amnestic identities. In the discussion, parallels between apparent amnesia in DID and state-dependent memory are drawn, and the question of simulated amnesia is addressed.

Ellert R. S. Nijenhuis, Philip Spinhoven, Johan Vanderlinden, Richard van Dyck and Onno van der Hart (1998)
Somatoform Dissociative Symptoms as Related to Animal Defensive Reactions to Predatory Imminence and Injury
Journal of Abnormal Psychology, Vol. 107, Issue 1 , Febr. 1998, 63-73

Abstract: The authors hypothesized that there would be a similarity between animal defensive responses to variable predatory imminence and injury and certain somatoform dissociative symptoms of trauma-reporting patients who have dissociative disorder. As a first test of this hypothesis, 12 somatoform symptom clusters consisting of clinically observed somatoform dissociative phenomena were constructed. All clusters discriminated between patients with dissociative disorders (n = 50) and patients with other psychiatric diagnoses (n = 50). Those expressive of the hypothesized similarity-freezing, anesthesia-analgesia, and disturbed eating-belonged to the 5 most characteristic symptoms of dissociative disorder patients. Anesthesia-analgesia, urogenital pain, and freezing symptom clusters independently contributed to predicted presence of dissociative disorder. Using an independent sample, it appeared that anesthesia-analgesia best predicted presence of dissociative disorder after controlling for symptom severity. The results were largely consistent with the hypothesized similarity.

Ellert R. S. Nijenhuis, Philip Spinhoven, Richard van Dyck, Onno van der Hart and Johan Vanderlinden (1998)
Psychometric Characteristics of the Somatoform Dissociation Questionnaire: A Replication Study
Psychother Psychosom 1998;67:17-23
DOI: 10.1159/000012254

Abstract: Background: The present study aimed to replicate the results of previous studies concerning the development of two versions of the Somatoform Dissociation Questionnaire. The SDQ-20 evaluates the severity of somatoform dissociative phenomena, and the SDQ-5 is a dissociative disorders screening instrument. Methods: Thirty-one patients with dissociative disorders and 45 consecutive psychiatric outpatients with other DSM-IV diagnoses completed the SDQ-20 and SDQ-5 as well as the Dissociation Questionnaire which measures psychological dissociation. Results: Mokken scale analysis showed that the items of the SDQ-20 are strongly scalable on a latent unidimensional scale. Internal consistency was high. The SDQ-20 convergent validity was supported by high intercorrelations with the DIS-Q. Dissociative patients obtained significantly higher scores than comparison patients. Patients with dissociative identity disorder scored significantly higher compared to patients with dissociative disorder nos. Sensitivity (94%) and specificity (98%) of the SDQ-5 were very satisfactory, as were, at an estimated prevalence rate of dissociative disorders of 10% among psychiatric patients, positive predictive value (84%) and negative predictive value (99%). Conclusions: All results replicated the first findings, and therefore corroborate the conclusion that the SDQ-20 and SDQ-5 are instruments of sound psychometric quality, and that somatoform dissociative phenomena are core symptoms of complex dissociative disorders.

Ellert R. S. Nijenhuis, Philip Spinhoven, Richard van Dyck, Onno van der Hart and Johan Vanderlinden (1998)
Degree of somatoform and psychological dissociation in dissociative disorder is correlated with reported trauma.
J Trauma Stress. 1998 Oct;11(4):711-30.

Abstract: In this study, the prevalence and severity of traumatic experiences as reported by patients with dissociative disorders and with other DSM-IV psychiatric diagnoses were compared. Furthermore, the predictive value of emotional, physical, and sexual trauma with respect to somatoform and psychological dissociation was analyzed. In contrast with comparison patients, dissociative disorder patients reported severe and multifaceted traumatization. Physical and sexual trauma predicted somatoform dissociation, sexual trauma predicted psychological dissociation as well. According to the memories of the dissociative disorder patients, this abuse occurred in an emotionally neglectful and abusive social context. Pathological dissociation was best predicted by early onset of reported intense, chronic and multiple traumatization. Methodological limitations restricting causal inferences between reported trauma and dissociation are discussed.