Abstract
We thank Dr Barry-Walsh for his interest in our article and for raising the issue of iatrogenesis in dissociative identity disorder (DID).
Dr Barry-Walsh argues that DID is a culture bound phenomena, created by social forces and overzealous North American DID-enthusiasts (i.e. iatrogenesis). In the first paragraph of his letter he cites as evidence of this belief the ICD-10's [1] comment that ‘this disorder is rare, and controversy exists about the extent to which it is iatrogenic or culture specific’ (italics added). This statement makes reference to the controversy, particularly prevalent before the ICD-10's publication in the early 1990's, rather than whether DID is an iatrogenic or culture-bound condition. We assume that the ICD-10's conclusion regarding the rarity of DID was made without awareness of, and in some cases before, the publication of the many DID prevalence studies from around the world (e.g. [2]). Dr Barry-Walsh also notes as evidence for the iatrogenesis of DID the New Oxford Textbook of Psychiatry's sceptical stance on the existence of DID. He failed to mention that the author of the chapter addressing DID (Dr Merskey) is a well known opponent of the condition. Consequently citing a chapter written by Dr Merskey as evidence that the condition does not exist is like citing a chapter by David Irving, the well-known Nazi holocaust revisionist historian, as evidence that the holocaust has been massively overstated. Finally, Dr Barry-Walsh cites as evidence for his belief in the culture-specific iatrogenesis of DID a survey of North American Psychiatrists' attitudes towards the condition. This study makes no attempt to address the scientific and psychiatric reality of DID, and it seems unusual that it would be cited as evidence against the validity of the condition.
Conspicuously absent from the evidence Dr Barry-Walsh cites in favour of iatrogenesis is scientific data (incidentally, the same comments can made about Dr Merskey's chapter in the New Oxford Textbook of Psychiatry). We are curious why Dr Barry-Walsh made no reference to the empirical studies which have examined the validity of DID as a psychiatric entity. For example in 2001 Gleaves, May & Cardeña [3] published a review paper on the validity of DID in Clinical Psychology Review. Utilizing several different standards for psychiatric validity, they found that DID was not only a valid psychiatric condition, but with the mass of empirical data accrued on its existence over the past quarter century the evidence for its validity was greater than several well-accepted psychiatric conditions. Given Dr Barry-Walsh's argument for the culture-specific (i.e. North America) nature of DID, it is perhaps not surprising that he failed to mention the large series research studies on DID that have been published from Australia, the Netherlands, Turkey, South America, Germany, Japan, and other countries. Many of these studies employed the Structured Clinical Interview for DSM-IV-Dissociative Disorders (SCID-D) or the Dissociative Disorders Interview Schedule (DDIS), two structured interviews for the gold standard detection of dissociative disorders, including DID.
Historically, the first cases of DID in the medical literature date from 1791 [4] and interest and clinical understanding in the diagnosis grew until the early 1900s. At this point the horizontal model of mind which had dominated psychiatric theory and practice, and which better explained DID, was replaced by Freud's topographical (vertical) model of mind. As is often the case when scientific paradigms change, the phenomena studied as part of the old paradigm cease to be a central focus and attention is redirected towards phenomena explained by the new paradigm [5]. In addition, various other factors, such as the construct of schizophrenia, drew attention away from DID [6]. The 1970s witnessed an incremental increase in the study of DID and following the dissociative disorders being liberated from hysterical neurosis and gaining independent status in DSM-III [7], the empirical study of DID proliferated. It is not surprising that clinical awareness of DID in the modern era principally arose in North America. Between 1987 and 2001 North America was responsible for 64% of the world's scientific publications on psychological trauma [8]. Dr Barry-Walsh makes no reference to the hundreds of scientific studies of DID including those more recently using neuroimaging (e.g. Reinders et al. [9] studied 11 DID participants using positron emission tomography technology). Instead he exclusively makes reference to the very much smaller sceptical literature on DID which has been dominated by theoretical conjecture and opinion rather than scientific data (e.g. see Merskey's chapter in the New Oxford Textbook of Psychiatry [10]).
Dr Barry-Walsh suggests that by using DID participants to study DID we have been scientifically ‘uncritical’ (‘I am … troubled by research which uncritically accepts as valid, diagnoses such as DID’). We concur with Dr Barry-Walsh that the study of psychiatric conditions must maximize the likelihood that participants in any study actually have the disorder they are sampled to represent. For this reason, as can be seen in our method section, we insisted that inclusion criteria for the DID participants was a psychiatrist's diagnosis of DID as well as an independent diagnosis of DID using the DDIS. It is also curious to us that in referring to our paper Dr Barry-Walsh made no reference to our data and the findings that the DID sample did not show exactly the same working memory profile as the PTSD and depressed groups and had a completely distinct profile from the psychosis group.
Our response to Dr Barry-Walsh's comments regarding the Dissociative Experiences Scale (DES) are limited to two points. Firstly, we cite one of the many studies that highlight the impressive psychometric properties of the instrument [11]. Secondly, no serious student of DID, including the authors of the DES [12] have suggested that the DES be used as a diagnostic instrument for DID, rather it was designed to quantify dissociative experiences and symptoms.
Dr Barry-Walsh claims that Pierre Janet, the late 19th, early 20th century French philosopher and psychiatrist, who developed the most advanced theory of dissociation of his time, ‘resiled’ his belief in DID. Yet neither in Janet's original work nor the meticulously detailed reviews of his large body of psychiatric writings (e.g. [13]) is there any indication that he recanted his dissociation theory nor his belief in DID. For example, in one of his later papers, reviewing his life's work, he comments that after the death of Charcot ‘hysteria patients (the condition which DID was subsumed under) seemed to disappear because they were now designated by other names. It was said that their tendency towards dissimulation and suggestibility made an examination dangerous and interpretations doubtful. I believe these criticisms to be grossly exaggerated and based on prejudice and misapprehension, and I am still under the illusion that my early works were not in vain and that they have left some definite ideas [14], p.127].’ Interestingly the philosopher (not a psychiatrist) whom Dr Barry-Walsh cites (Dr Hacking) in favour of his view regarding Janet's dismissal of his dissociation theory has himself been criticised for his superficial scholarship of Janet's original work [15].
Dr Barry-Walsh ends his letter with a challenge to clinicians and researchers to answer what he describes is the ‘fundamental question’ of ‘why (DID has) so much currency in some circles yet (has) none in others.’ In light of the scientific evidence accrued over the last 25 years in support of the diagnosis, and its continued prominent inclusion in the world's most widely used nosological system, a more pertinent question is why in the face of overwhelming empirical evidence from around the world do some clinicians still continue to deny the existence of DID?