Andrew Moskowitz, Ph.D. Department of Mental Health, University of Aberdeen Aberdeen, Scotland a.moskowitz@abdn.ac.uk Are psychotic symptoms traumatic in origin and dissociative in kind? Summary of a paper presented at the 22nd ISSD conference, Toronto, November 2005. Based on a chapter in Dissociation and the Dissociative Disorders: DSM-V and Beyond, Paul Dell and John O’Neill, Eds. (submitted for publication).Chapter co- authors: John Read, Susie Farrelly, Thom Rudegeair and Ondra Williams. While there is an entrenched clinical belief that ‘dissociative’ voices differ from ‘psychotic’ voices… there is no compelling evidence that this is so. Despite increasing interest in the relationship between trauma and psychosis, relatively little attention has been paid to the potentially mediating role of dissociation. The important role dissociative processes may play in the development of psychotic symptoms is explored below. Over the past several years, there has been considerable discussion about the relationship between the diagnosis of schizophrenia and dissociative disorders (and processes). The dramatic decrease of interest in multiple personality and associated disorders at the beginning of the 20th century has been attributed to Bleuler’s 1911 concept of schizophrenia (Rosenbaum, 1980), which substantially broadened Kraepelin’s ‘dementia praecox’ to include a wide range of apparently dissociative phenomena. Indeed, Colin Ross (2004) has recently argued that some of the cases Bleuler described as ‘schizophrenic’ would be considered DID today, and I have been tracing the influence of Pierre Janet and allied dissociationists on the development of Bleuler’s ideas (Moskowitz, 2006). Issues of comorbidity between dissociative, (other) post-traumatic, and psychotic disorders have been the focus of dozens of studies and papers, resulting in proposals for a psychotic subtype of PTSD and a dissociative subtype of schizophrenia, and measures of dissociation and psychoticism have been shown to be highly correlated in numerous populations (Moskowitz, Barker-Collo & Ellson, 2005). Here, we take a different approach to exploring the apparently close relationship between dissociation and psychosis. As the broadest definition of psychosis in the DSM-IV is simply all the symptoms of schizophrenia – excluding ‘negative’ symptoms –we decided to examine each of the ‘positive’ symptoms making up this diagnosis and consider the extent to which dissociative processes could be employed to understand them. In addition, we considered whether research findings on cognitive impairment and brain dysfunction in schizophrenia would be consistent with a dissociative interpretation of these symptoms. A diagnosis of DSM-IV schizophrenia (American Psychiatric Association, 1996) requires two of the following five symptoms: • delusions • hallucinations