Psychosis, trauma and dissociation: evolving perspectives on severe psychopathology

The revised and updated second edition of Psychosis, trauma and dissociation: Evolving perspectives on severe psychopathology (Moskowitz, Dorahy, & Schäfer, 2019) is an ambitious book whose main goal is to provide an understanding of the links in clinical practice of three main concepts: trauma, dissociation and psychosis. The book is divided into three parts. The initial chapters review the historical background of dissociation, trauma, psychosis (schizophrenia) and other related concepts (e.g. hysteria). Throughout the initial chapters (Chapters 1 to 5), the authors argue for a return to historical definitions of dissociation and psychosis (e.g. Janet and Bleuler) and that psychosis (or at least some psychotic experiences; e.g. voice-hearing) is dissociative in nature. Here dissociation is not considered in its more common and broad contemporary meaning (i.e. ‘a lack of integration of psychological functions’, Chapter 1, p. 19). Instead, authors focus mostly on structural dissociation of the personality and its traumatic nature, again harking back to the concept’s historical roots (but see Lynn et al., 2014). The important role of adverse experiences in the development of dissociation, borderline personality disorder (Chapter 6) and psychosis is also highlighted. The latter, authors argue, should not be understood as ‘incomprehensible’ experiences (Chapter 1, p.10), but instead within the individual’s life context, particularly past traumatic/adverse experiences.

Part two of the book explores a wide range of research perspectives on the relationship between trauma, dissociation, and psychotic phenomena including the prevalence of childhood trauma (Chapter 9) and dissociative phenomena (Chapter 11) in psychosis and the prevalence of psychotic symptoms in dissociative disorders. Indeed, childhood trauma is an important environmental risk factor for psychosis (e.g. Varese et al., 2012) and some preliminary data suggest that dissociation might be one of the psychological mechanisms mediating the association between trauma and psychosis (Williams, Bucci, Berry, & Varese, 2018). Recently, a scale was developed to specifically assess trauma in people with psychosis to better understand these overlaps (Carr, Hardy, & Fornells-Ambrojo, 2018). Chapter 10 describes specifically the structural brain changes following adversity compared to changes seen in psychotic and dissociative disorders. Together, these chapters highlight high prevalence rates, symptom and diagnostic overlaps, and overlaps in terms of changes in brain structures. It is suggested that dissociative disorders and psychosis occur on a continuum of responses to trauma. However, this is largely based on clinical anecdote and not yet backed up by research evidence. This idea is also explored in Chapter 13 by Longden et al., who introduce their theory of voice-hearing as dissociated self states and outline some evidence supporting this theory. The overlap between psychosis and PTSD is also explored in this section of the book, with a proposal of a psychotic PTSD subtype (Chapter 16). Another interesting overlap not covered in the book is the recent recognition that PTSD commonly occurs in response to psychosis and associated experiences (Fornells-Ambrojo, Gracie, Brewin, & Hardy, 2016). Finally, the subsequent chapters explore the role of memory and attention processes in schizophrenia and PTSD (Chapter 17) as well as dissociation and psychosis (Chapter 18). Together, they highlight that similar cognitive processes seem to be altered across these disorders.

Part three mainly addresses the relation between dissociation and psychosis. The two first chapters (Chapters 19 and 20) argue in favour of new diagnostic categories: Dissociative Psychosis and Dissociation subtype of schizophrenia. Although authors provide relevant arguments favouring their proposition, further research is needed since evidence of these categories’ existence remains scarce. These are followed by two chapters on how clinical assessment allows for differential diagnosis of dissociative disorders and schizophrenia. Evidence points out that the Structured Clinical Interview for Dissociative Disorders, the Wechsler Adult Intelligence Scale and other personality tests with validity scales (e.g. MMPI-2) can clearly differentiate both samples. Some chapters are also dedicated to describing psychological approaches to understand and treat psychosis and related experiences including the Maastricht Approach (Chapter 24) to understand voice-hearing, the Eye Movement Desensitization and Reprocessing (EMDR) therapy to treat individuals with psychosis and PTSD (Chapter 25), and the psychodynamic approach (Chapter 26). The efficacy of the latter is yet to be backed by empirical evidence, but a recent systematic review has endorsed the safety and feasibility of EMDR for psychosis (Adams, Ohlsen, & Wood, 2020). Other trauma-focused treatments (e.g. Exposure therapy) are also alternatives to treat PTSD in psychosis (Sin & Spain, 2017), but are not explored in this book. The final chapter addresses how individuals give meaning to their voice-hearing and dissociative experiences (among others – out of the ordinary experiences) and how this takes places within a social and cultural context.

In sum, the book provides a very detailed and comprehensive overview of the links and overlaps between the concepts of dissociation, trauma, and psychosis. The different chapters examine this topic from multiple perspectives and at several levels of understanding (historical, phenomenological, neurobiological, and clinical). Concepts which many clinicians and researchers may take for granted are dismantled and explored in-depth, meaning that readers are forced to question any preconceptions.

The definition of the term dissociation is identified to be complex and contentious throughout the book. Indeed different chapters focus on different aspects of dissociation. It is notable that much of the empirical evidence regarding the prevalence and mediating role of dissociation in psychotic experiences uses a broad definition of dissociation (Pilton, Varese, Berry, & Bucci, 2015), rather than the more narrow version of structural dissociation that is the emphasis of much of the theoretical material introduced in the book. This highlights the need for more empirical evidence to examine theoretical models that see psychotic symptoms as dissociative in the more specific use of the term.

This book will be of interest to researchers, clinicians, and people with lived experience wanting to explore the relationship between trauma, dissociation and psychosis in detail. It will be suited to people who are willing to dismantle preconceptions and embrace these concepts’ complexity.

Overall, the book explores new ways to understand trauma, psychosis and dissociation and open further research areas, which can benefit clinicians and, in particular, people with lived experiences of voice-hearing, psychosis, dissociation and who have been impacted by traumatic events.