Historical and current research on borderline personality disorder reveal certain affinities with schizophrenia spectrum psychopathology. This is also the case for the borderline criteria of "identity disturbance" and "feelings of emptiness," which reflect symptomatology frequently found in schizophrenia and schizotypal personality disorder. Unfortunately, the diagnostic manuals offer limited insight into the nature of these criteria, including possible deviations and similarities with schizophrenia spectrum symptomatology. In this article, we attempt to clarify the concepts of identity disturbance and feelings of emptiness with an emphasis on the criteria's differential diagnostic significance. Drawing on contemporary philosophy, we distinguish between a "narrative" self and a "core" self, suggesting that this distinction may assist differential diagnostic efforts and contribute to mark the psychopathological boundaries of these disorders.

The status of borderline personality disorder (BPD) as a diagnostic category is a matter of continuing controversy. In the United States, BPD is one of the most frequent diagnoses of psychiatric inpatients, and a similar tendency emerges in Europe. Nearly all theoretical aspects of BPD have been questioned, including its very position as a personality disorder. In this article, we trace the evolution of the borderline concept from the beginning of the 20th century to the current psychometric research. We argue that the status of BPD is fraught with conceptual difficulties, including an unrecognized semantic drift of major phenomenological terms (e.g., identity), a lack of general principles for the distinction of BPD and the major psychiatric syndromes (e.g., schizophrenia spectrum disorders), and insufficient definitions of key nosological concepts. These difficulties illustrate general problems in today's psychiatry that require consideration.

We have previously argued that the current borderline personality disorder (BPD) diagnosis is over-inclusive and clinically and conceptually impossible to distinguish from the schizophrenia spectrum disorders. This study involves 30 patients clinically diagnosed with BPD as their main diagnosis by three BPD dedicated outpatient treatment facilities in Denmark. The patients underwent a careful and time-consuming psychiatric evaluation involving several senior level clinical psychiatrists and researchers and a comprehensive battery of psychopathological scales. The study found that the vast majority of patients (67% in DSM-5 and 77% in ICD-10) in fact met the criteria for a schizophrenia spectrum disorder, i.e., schizophrenia (20%) or schizotypal (personality) disorder (SPD). The schizophrenia spectrum group scored significantly higher on the level of disorders of core self as measured by the Examination of Anomalous Self-Experiences Scale (EASE). The BPD criterion of "identity disturbance" was significantly correlated with the mean total score of EASE. These findings are discussed in the light of changes from prototypical to polythetic diagnostic systems. We argue that the original prototypes/gestalts informing the creation of BPD and SPD have gone into oblivion during the evolution of polythetic criteria.

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Disordered selfhood in schizophrenia was rediscovered at the turn of the millennium. In 2005, <i>Psychopathology</i> published the psychometric instrument, the Examination of Anomalous Self-Experience (EASE). In this article, we summarize the historical background of the creation of the EASE, explicate the notion of the disorder of basic or minimal self with the help of phenomenological philosophy, and provide a brief description of clinical manifestations targeted by the EASE. We also present our personal experience using and teaching the EASE and summarize the empirical evidence obtained so far. We conclude that the basic self-disorder represents a crucial phenotype of schizophrenia spectrum disorders and that this phenotype offers a potential avenue to empirical pathogenetic research and psychotherapeutic treatment.