Theoretically informed, prototypical diagnostic models of psychosis: a narrative review

Introduction: Although psychotic disorders have been intensively studied for more than a century, with a bewildering accumulation of empirical data, we still have only a very partial understanding of their diagnostic boundaries and etiopathogenesis. The relative lack of etiological and therapeutic progress has been partly attributed to the DSM's rigid "neo-Kraepelinian" descriptive, symptom- focused classification relying on present-versus-absent diagnostic criteria, mostly delusions, hallucinations, and Schneiderian first-rank symptoms. This approach, which overly on criteria potentially sacrifices validity for reliability, has at least three main limitations: 1) it affects differential diagnosis and improves comorbidity as an artifact of the excessive splitting of closely related clinical conditions; 2) milder forms of schizophrenia that would have previously been considered latent, borderline, or pseudoneurotic have struggled to claim a proper diagnostic location (Lingiardi & Boldrini, 2018), and, more importantly; 3) it fail to grasp clinical manifestations that may be detectable at premorbid phases of the illness and that may reflect or constitute generative disorders at the core of the illness. These limitations underscore the need to consider what Kendler (1990) has called "non- empirical aspects of validity"—namely, the way in which a disease entity is conceptualized in the first place (Nordgaard et al., 2013). In the current narrative review, we aimed at reviewing the available literature on theoretically informed, prototypical diagnostic models of psychosis, not based on a number of specific psychotic symptoms, but rather relied on the identification of characteristic traits or gestalt. Method: We searched PubMed, Web of Science, and PEPweb for papers published until June 2022. Additional publications were identified in the references cited in the initial papers. We selected only studies on definitions of psychosis from any theoretical background, which have been operationalized through psychometric measures later used for generating empirical evidence on external and prognostic validity. We used theoretical considerations to characterize approaches and noted empirical findings. Results: In the psychodynamic literature, the terms psychosis and psychotic functioning primarily refer to the behavioral manifestations of patients who have lost the capacity for "reality testing" (Kernberg, 2019). The term reality testing was originally introduced by Freud (1911) as a kind of trial- and-error approach to mapping the contours of reality. Later, it has been redefined within psychoanalytic object relations theory as the ability to differentiate self from non-self, intrapsychic from external origin of stimuli, and the capacity to maintain empathy with ordinary social criteria for reality (Kernberg, 1984; Oyebode, 2018). In Kernberg's model of structural diagnosis, the loss of reality testing is the unique criteria for differentiating psychotic personality organizations from borderline personality organizations, giving even more importance to this clinical concept. A standardized measure for psychotic personality organization has been validated, namely the Structured Interview of Personality Organization (STIPO), developed by Kernberg's group (Clarkin et al., 2004). However, not any empirical study has been conducted on its external and prognostic validity. The diagnostic insight of a "psychotic level of organization" has also been included in the Psychodynamic Diagnostic Manual (PDM-2; Lingiardi & McWilliams, 2017), due to its clinical utility of conceptualizing a psychotic range of functioning. A psychotic level of personality organization implies identity diffusion, poor differentiation between representations of self and others, poor discrimination between fantasy and external reality, reliance on primitive defenses, and deficits in reality testing. The Psychodiagnostic Chart-2 (PDC-2) is a PDM-2 derived validated clinician-rated measure allowing for psychometrically assessing the psychotic level of organization. Even in this case, no empirical studies have been conducted applying this measure to assess the external and prognostic validity of the psychotic level of organization, probably since the instrument has been proposed relatively recently. Regarding the academic phenomenology tradition, the "ipseity-self model" has been developed, accounting for the so-called self-disorders that are considered as the pathogenic core of psychotic disorders. Self-disorders (also termed anomalous self-experiences or basic self-disturbances) can be depicted as long-lasting non-psychotic experiences and distortions in subjectivity. They include changes in self-experience such as a failing sense of self-presence and feelings of not being truly present in the world, bodily self-alienation and the permeability of ego-boundaries, "hyper-reflexivity" (i.e., an exaggerated self-consciousness), and "disturbed grip or hold" to the world. A semi-structured psychometric instrument for a systematic, qualitative, and quantitative assessment of self-disorders was published— namely, the Examination of Anomalous Self-Experience (EASE; Parnas et al., 2005) scale. Empirical studies using the EASE scale have been conducted worldwide, exploring non-psychotic self-disorders and their association with other clinical variables, such as diagnostic outcomes and major symptom clusters (e.g., positive, negative, and disorganized). The results consistently show that self-disorders hyper-aggregate in schizophrenia spectrum disorders but not in other mental disorders; that self-disorders are found in individuals at a clinical risk of developing psychosis; that self-disorders predict the later development of schizophrenia spectrum disorders; and that self- disorders correlate with the canonical dimensions of the psychopathology of schizophrenia, impaired social functioning, and suicidality (Henriksen et al., 2021). Conclusion: We found two major theoretically informed, prototypical diagnostic models for psychosis, the "psychotic level of organization" and the "ipseity-self model", from the psychodynamic and phenomenological traditions, respectively. Both of them agree on the loss of capacity to distinguish self from the non-self as a prototypical feature of psychotic disorders – defined as "loss of reality testing" in psychodynamic diagnosis, and as "transitivistic phenomena" in the "ipseity-self model". More research in the psychodynamic field is needed. Epistemological and clinical insights, also for a potential integration between the two models, will also be discussed with reference to the updates planned for the third edition of the PDM.