Review
Structure of the psychotic disorders classification in DSM‐5

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Abstract

Schizophrenia spectrum disorders attract great interest among clinicians, researchers, and the lay public. While the diagnostic features of schizophrenia have remained unchanged for more than 100 years, the mechanism of illness has remained elusive. There is increasing evidence that the categorical diagnosis of schizophrenia and other psychotic disorders contributes to this lack of progress. The 5th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) continues the categorical classification of psychiatric disorders since the research needed to establish a new nosology of equal or greater validity is lacking. However, even within a categorical system, the DSM-5 aims to capture the underlying dimensional structure of psychosis. The domains of psychopathology that define psychotic disorders are presented not simply as features of schizophrenia. The level, the number, and the duration of psychotic signs and symptoms are used to demarcate psychotic disorders from each other. Finally, the categorical assessment is complemented with a dimensional assessment of psychosis that allows for more specific and individualized assessment of patients. The structure of psychosis as outlined in the DSM-5 may serve as a stepping-stone towards a more valid classification system, as we await new data to redefine psychotic disorders.

Introduction

Schizophrenia is a classic psychiatric diagnosis. The defining features have remained unchanged for more than 100 years (Heckers, 2011). However, emphasis has shifted from avolition and dissociation towards reality distortion (Fischer and Carpenter, 2009). The diagnosis attracts great interest among clinicians, researchers, and the lay public. Schizophrenia is associated with significant bias and stigma, leading some to ask for the removal of the word from diagnostic manuals (Umehara et al., 2011). But even those who prefer a different name do not doubt that schizophrenia is real (Lieberman and First, 2007).

Despite sustained effort, the mechanism of schizophrenia has remained elusive. There is increasing evidence that the categorical diagnosis of schizophrenia and other psychotic disorders contributes to this lack of progress (Heckers, 2008). The current diagnoses do not accurately capture the considerable variability of symptom profile, response to treatment, and most importantly, social function and outcome. As a result, there is increasing pressure to change the structure of psychiatric nosology, in order to accelerate better treatment, prevention, and ultimately cure (Cuthbert and Insel, 2010, Insel, 2010).

The 5th edition of the DSM does not represent such a paradigm shift. While there was considerable hope to replace the categorical diagnosis of psychiatric disorders, the research needed to establish a new nosology of equal or greater validity is lacking (Hyman, 2007, Kupfer and Regier, 2011). So far, the mechanistic models of brain and behavior provided by systems and basic neuroscience research have not been adequately tested in clinical settings. Nonetheless, despite the inherent conservative bias, the DSM-5 chapter “Schizophrenia Spectrum and Other Psychotic Disorders” (referred to as Schizophrenia Spectrum for short in the rest of this article) departs from the previous edition in several respects. Even within the established categorical system, we want to capture the underlying dimensional structure of psychosis. To that effect, we employ the terms domains, gradients, and dimensions. There are five domains of psychopathology that define psychotic disorders. The level of psychosis, the number of symptoms, and the duration of psychosis are the gradients that have been used to demarcate psychotic disorders from each other and continue to be used for the same purpose in DSM-5. The dimensions refer to a structure of psychosis that is not simply categorical but allows for much greater flexibility in the assessment of psychopathology, including aspects that are not considered as defining domains of psychosis.

Here, we describe the structure of the chapter on “Schizophrenia Spectrum and Other Psychotic Disorders” in the DSM-5. We review the domains of psychopathology that define psychosis, clarify the status of catatonic features, and describe the greater emphasis on dimensions incorporated into the DSM-5.

Section snippets

Domains of psychopathology

The most visible change in the schizophrenia spectrum chapter is the less prominent position of schizophrenia. DSM-IV puts schizophrenia front and center. All the classic features of psychotic disorders are introduced in the section on schizophrenia and are not presented again in the subsequent description of other psychotic disorders. This reaffirms schizophrenia as the paradigmatic disorder associated with hallucinations, delusions, disorganization of speech, disorganized behavior, and

Gradients of psychosis

The signs and symptoms of psychosis are on a continuum with normal mental states (Allardyce et al., 2007). While some presentations are unequivocally beyond the most liberal spectrum of mental health, many presentations are subtle and the demarcation of the psychotic from the normal mental state is difficult. Assessment for the presence of psychosis should consider whether beliefs are flexible; whether perceptions are linked to an external stimulus; whether thoughts are logical, coherent, and

Dimensions of psychosis

Dimensional assessments capture meaningful variation in the severity of symptoms, which may help with treatment planning and the prediction of course and outcome (Allardyce et al., 2007). It is also the hope that dimensional approaches will accelerate the study of disease mechanisms and ultimately the development of interventions to prevent and cure psychotic disorders (Heckers, 2008). In the DSM-5, we propose that a patient who presents with the signs and symptoms of psychosis should be

Conclusion

The discovery process in psychiatry is slow. Despite significant investments over the last 100 years, the mechanism of psychosis has eluded us. While the emerging technologies of neuroscience and genetics have provided us with greater access to patients at the level of genes, protein, cells, and circuits, these new data have been connected only loosely to the well-known domains of psychopathology. It is likely that the current nosology of psychotic disorders is not an adequate template for the

Conflict of interest

The authors have declared all relevant conflicts of interest regarding their work on the DSM-5 Psychotic Disorders work group to the APA on an annual basis. The complete details are posted on the public Web site http://www.dsm5.org/MeetUs/Pages/PsychoticDisorders.aspx.

Acknowledgment

The authors do not have to declare any funding or administrative support for this manuscript.

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