Schizophrenia Spectrum Disorders: An Empirical Benchmark Study of Real-world Diagnostic Accuracy and Reliability Among Leading International Psychiatrists.

Background and hypothesis: Assigning a psychiatric diagnosis in real-world situations is often difficult, given that the clinical presentation does not usually conform to the list of condensed, simplified behavioral descriptors of mainstream operational taxonomies (MOT) (eg, ICD-11 and DSM-5). The goal of this study was to benchmark diagnostic accuracy and reliability on a central and severe spectrum of psychopathology (ie, the schizophrenia spectrum disorders [SSDs]), adopting a pragmatic approach as close as possible to real-world clinical settings. Study Design: We examined the diagnostic performance of 30 international psychiatrists experts in SSD. The clinicians were asked to make their clinical best diagnostic estimate for two written clinical vignettes excerpted from real-world SSD cases. Study Results: In the first vignette, 22 out of the 30 clinicians (73.5%) indicated a SSD as their main diagnostic hypothesis. In the second vignette, 12 clinicians (40%) chose SSD as their main diagnostic hypothesis. Only 10 of the 30 clinicians (33%) correctly identified both vignettes as cases of SSD. The level of interrater diagnostic agreement (Fleiss' Kappa) was low but statistically significant (KFleiss = 0.08, P = .01). Conclusions: The results suggest that, even in a sample of influential international psychiatrists, the diagnostic accuracy and reliability on SSD presentations is poor and substantially inferior to those obtained in reliability studies using structured or semi-structured interviews. The widespread adoption of MOT systems in the last decades may have inadvertently eroded the ability of clinicians to detect a typical pattern of psychiatric illnesses.

An Empirical-Phenomenological Exploration of Anderssein (Feeling Different) in Schizophrenia: Being in-between Particular and Universal.

INTRODUCTION: In this paper, we wish to elucidate alterations of basic existential and intersubjective configurations in schizophrenia spectrum disorders (SSD) through the phenomenon of Anderssein ("feeling different"). Anderssein is an important yet neglected notion from German psychiatry, referring to a specific sense of feeling profoundly different from others occurring in SSD. Although phenomenological-psychopathological research mentions it as an aspect of the core disturbance of SSD (namely, "self-disorders"), the phenomenon has not yet been explored in empirical or theoretical detail. METHOD: We present material from a phenomenological-empirical study on the mode and onset of psychosis based on qualitative interviews with 25 patients with SSD. RESULTS: Most of the participants in our study report having felt fundamentally and often ineffably different since childhood and articulate it as a sense of existing "outside" of the shared reality. Intersubjective reality appears progressively unreal or inauthentic, and simultaneously, the patient's intimate, subjective sphere is permeated by an alien otherness. Importantly, this outside position should be understood carefully as it is often accompanied by the sense of being invaded by social rules, other people's thoughts, or emotions. Incipient psychosis is described as a gradual extension of precedent alterations of the structures of (inter)subjectivity. CONCLUSION: We conceptualize the ontological feature of Anderssein as an altered "being in-between" - that is, some sort of halting of the dynamic movement between particularity and intersubjectivity. Finally, we discuss the critical implications of these results for research into the "onset" of schizophrenia.

Altered cardiac autonomic functioning associates with self-disorders in schizophrenia.

Elevated resting heart rate (RHR) and reduced heart rate variability (HRV) are signs of autonomic nervous system dysfunction identified in schizophrenia (SCZ). This dysfunction has been found to manifest prior to the onset of the clinical diagnosis. Yet whether such autonomic dysfunction is associated with vulnerability to schizophrenia remains unknown. This case-control study included recent onset SCZ patients (n = 35) and healthy controls (HC) (n = 33). Patients were scored for self-disorders (SD's) using the EASE manual and all participants underwent a 5-minute resting state electrocardiogram (ECG) recording. Patients were included from outpatient clinics in Denmark. The main measures comprised EASE total scores (SDs), RHR (beats per minute) and three standard HRV measures usually included in testing autonomic nervous system dysfunction: root mean squared of successive differences (RMSSD), standard deviation of normal-to-normal interval (SDNN) and high-frequency/ low frequency ratio (HF/LF). Pearson correlations and linear regression models adjusted for age, sex and medication were used in the SCZ group. The main finding was a positive moderate association between SDs and RHR (r = 0.463; p = 0.005) and a negative association between SDs and HRV (RMSSD) (r = -0.440; p = 0.008) in the SCZ group. Linear regression models found SDs to explain 22 % of the variance of RHR and 19 % in RMSSD. SDs correlated with LF/HF (r = 0.434; p = 0.009), but non-significantly with SDNN. The study provides evidence of an intriguing link between SDs as a susceptibility trait for schizophrenia spectrum disorders and altered cardiac autonomic functioning.

The phenomenological nature of schizophrenia and disorder of selfhood.

Schizophrenia continues its resistance to the pathogenetic understanding. We believe that one of the reasons is an oblivion of schizophrenia's characteristic Gestalt expressive of its psychopathological structure. In this article we argue for a crucial role of disorders of selfhood in the constitution of this Gestalt. First, we present a phenomenological account of the self. This is followed by an exposition of basic complaints in schizophrenia which are reflective of a disordered selfhood and which often date back to childhood. We then present characteristic features of the schizophrenic psychosis with its phenomenon of "double bookkeeping". Hallucinations, delusions and double bookkeeping are all associated with the instability of the self. Finally, we briefly address characteristic aspects of the encounter with a schizophrenia patient and argue that self-disorders play an important diagnostic role. We conclude by emphasizing the role of phenomenology in psychiatric research.

Pseudoneurotic Symptoms in the Schizophrenia Spectrum: A Longitudinal Study of Their Relation to Psychopathology and Clinical Outcomes.

BACKGROUND AND HYPOTHESIS: Nonpsychotic symptoms (depression, anxiety, obsessions, etc.) are frequent in schizophrenia-spectrum disorders and are usually conceptualized as comorbidity or transdiagnostic symptoms. However, in twentieth century foundational psychopathological literature, many nonpsychotic symptoms with specific phenomenology (here termed pseudoneurotic symptoms) were considered relatively typical of schizophrenia. In this prospective study, we investigated potential associations of pseudoneurotic symptoms with diagnostic status, functional outcome as well as psychopathological dimensions of schizophrenia. STUDY DESIGN: First-admitted patients (N = 121) diagnosed with non-affective psychosis, schizotypal disorder, or other mental illness were examined at initial hospitalization and 5 years later with a comprehensive assessment of psychopathology. Informed by the literature, we constructed scales targeting pseudoneurotic symptoms and other, more general, nonpsychotic symptoms. STUDY RESULTS: Pseudoneurotic symptoms aggregated in schizophrenia-spectrum groups compared to other mental illnesses and occurred at similar levels at baseline and follow-up. They longitudinally predicted poorer social and occupational functioning in schizophrenia-spectrum patients over a 5-year-period but not transition to schizophrenia-spectrum disorders from other mental illnesses. Finally, the level of pseudoneurotic symptoms correlated with disorder of basic self at both assessments and with positive and negative symptoms at follow-up. The scale targeting general nonpsychotic symptoms did not show this pattern of associations. CONCLUSIONS: The study supports that a group of nonpsychotic symptoms, ie, pseudoneurotic symptoms, are associated with schizophrenia-spectrum disorders and linked with temporally stable psychopathology, particularly disorder of the basic self. Their prospective association with social and occupational functioning needs replication.

Phenomenology of auditory verbal hallucination in schizophrenia: An erroneous perception or something else?

This study presents phenomenological features of auditory verbal hallucinations (AVH) in schizophrenia and associated anomalies of experience. The purpose is to compare the lived experience of AVH to the official definition of hallucinations as a perception without object. Furthermore, we wish to explore the clinical and research implication of the phenomenological approach to AVH. Our exposition is based on classic texts on AVH, recent phenomenological studies and our clinical experience. AVH differ on several dimensions from ordinary perception. Only a minority of schizophrenia patients experiences AVH localized externally. Thus, the official definition of hallucinations does not fit the AVH in schizophrenia. AVH are associated with several anomalies of subjective experiences (self-disorders) and the AVH must be considered as a product of self-fragmentation. We discuss the implications with respect to the definition of hallucination, clinical interview, conceptualization of a psychotic state and potential target of pathogenetic research.

The self, neuroscience and psychosis study: Testing a neurophenomenological model of the onset of psychosis.

AIM: Basic self disturbance is a putative core vulnerability marker of schizophrenia spectrum disorders. The primary aims of the Self, Neuroscience and Psychosis (SNAP) study are to: (1) empirically test a previously described neurophenomenological self-disturbance model of psychosis by examining the relationship between specific clinical, neurocognitive, and neurophysiological variables in UHR patients, and (2) develop a prediction model using these neurophenomenological disturbances for persistence or deterioration of UHR symptoms at 12-month follow-up. METHODS: SNAP is a longitudinal observational study. Participants include 400 UHR individuals, 100 clinical controls with no attenuated psychotic symptoms, and 50 healthy controls. All participants complete baseline clinical and neurocognitive assessments and electroencephalography. The UHR sample are followed up for a total of 24 months, with clinical assessment completed every 6 months. RESULTS: This paper presents the protocol of the SNAP study, including background rationale, aims and hypotheses, design, and assessment procedures. CONCLUSIONS: The SNAP study will test whether neurophenomenological disturbances associated with basic self-disturbance predict persistence or intensification of UHR symptomatology over a 2-year follow up period, and how specific these disturbances are to a clinical population with attenuated psychotic symptoms. This may ultimately inform clinical care and pathoaetiological models of psychosis.

Double bookkeeping in schizophrenia spectrum disorder: an empirical-phenomenological study.

Double bookkeeping is a term introduced by Eugen Bleuler to describe a fundamental feature of schizophrenia where psychotic reality can exist side by side with shared reality even when these realities seem mutually exclusive. Despite increasing theoretical interest in this phenomenon over the recent years, there are no empirical studies addressing this issue. We have, therefore, conducted a phenomenologically descriptive qualitative study of 25 patients with schizophrenia in which we addressed the following issues: (1) Experience of double reality; (2) Emergence and development of two realities; (3) Truth quality of psychotic or private reality; (4) Insight into illness; (5) Communication of psychotic experiences. The most important result was that most patients felt to be in contact with another dimension of reality. Hallucinatory and delusional experience pertained to this different reality, which patients most frequently kept separated from the shared reality. This other dimension was considered by the patients as being more profound and real. The pre-psychotic and psychotic experiences were difficult to verbalize and typically described as totally different than ordinary experience. Double reality was persistent across remissions. None of the patients considered their condition as an illness analogous to a somatic disorder. Most patients described a vague sense of duality preceding the crystallization of double bookkeeping. This emergence of doubleness was associated with a fundamental alienation from oneself, the world, and others stretching back to childhood or early adolescence. We discuss the results with a special emphasis on the concept of psychosis, clinical interview, treatment, and pathogenetic research.

Are Self-disorders in Schizophrenia Expressive of a Unifying Disturbance of Subjectivity: A Factor Analytic Approach.

BACKGROUND AND HYPOTHESIS: The idea that a disorder of the basic self is a central feature in schizophrenia has recently been corroborated in a meta-analysis and a systematic review. Manifestations of the self-disorder can be systematically explored with the Examination of Anomalous Self-Experience (EASE). In this study, we examined the factorial structure of EASE, and diagnostic efficacy of EASE. We hypothesized that EASE will have a monofactorial structure as an instability of the basic self will result in multiple deformations of self-experience which would be meaningfully interrelated as aspects of a unifying Gestalt. DESIGN: EASE data for 226 patients suffering from various mental disorders were analyzed under a confirmatory factor analysis framework (CFA). Area under the receiver operating characteristic curve (AUC) was calculated for the total EASE sums, and sensitivity and specificity values for prediction of schizophrenia spectrum disorders based on different cut-offs were obtained. RESULTS: Fit indices for the CFA model: RMSEA = 0.036, SRMR = 0.100, CFI = 0.983, TLI = 0.981. The AUC value was 0.946 (95% confidence interval: 0.919-0.974). Sensitivity as well as specificity for schizophrenia spectrum disorders were high. CONCLUSION: Our results lend support for EASE exhibiting a monofactorial structure and the notion of self-disorders as a central phenotypic feature of schizophrenia spectrum disorders.

Pseudoneurotic symptoms in the schizophrenia spectrum: An empirical study.

BACKGROUND: Nonpsychotic symptoms (depression, anxiety, obsessions etc.) are frequent in schizophrenia-spectrum disorders. Twentieth century foundational psychopathological literature claimed that certain nonpsychotic symptoms (here termed pseudoneurotic symptoms) are relatively closely linked with the schizophrenia-spectrum, despite descriptive overlap with symptoms of other diagnoses. In this study, we investigated the association of pseudoneurotic and other nonpsychotic symptoms with the schizophrenia-spectrum as well as a hypothesis about an association of pseudoneurotic symptoms with disorder of basic self. METHODS: The sample (N = 226) comprised patients with non-affective psychosis (N = 119), schizotypal personality disorder (N = 51) and other mental illness (N = 56), who were examined with a comprehensive assessment of lifetime psychopathology. Informed by the literature, we constructed scales targeting pseudoneurotic symptoms and other, more general, nonpsychotic symptoms. RESULTS: Pseudoneurotic symptoms aggregated significantly in schizophrenia-spectrum disorders with an Area under the receiver operating characteristic curve of 0.84 (SE 0.03) for classifying patients with schizophrenia-spectrum disorders versus other mental illness. Patients with non-affective psychosis scored slightly, but significantly, higher on the scale targeting general nonpsychotic symptomatology than the other groups. In multiple regression analysis, pseudoneurotic symptoms were predicted by general nonpsychotic symptoms, disorders of basic self, and negative symptoms but not positive symptoms. CONCLUSION: The study supports that certain neurotic-like symptoms with specific descriptive features (pseudoneurotic symptoms) are associated with schizophrenia-spectrum disorders. It suggests that pseudoneurotic symptoms are linked with temporally stable schizophrenia psychopathology (disorder of basic self and negative symptoms).

Auditory Verbal Hallucinations in Schizophrenia, Part II: Phenomenological Qualities and Evolution.

ABSTRACT: Hallucination is defined in the diagnostic systems as an experience resembling true perception without causal stimulus. In this second report from an in-depth phenomenological study of schizophrenia patients experiencing auditory verbal hallucinations (AVHs), we focused on the phenomenological qualities of AVHs. We found that a substantial proportion of patients could not clearly distinguish between thinking and hallucinating. The emotional tone of the voices increased in negativity. AVHs became more complex. Spatial localization was ambiguous and only 10% experienced only external hallucinations. There was an overlap with passivity phenomena in one third of the cases. The patients occasionally acted upon the content of AVHs. In the discussion section, we criticize the perceptual model of AVHs. We conclude that the definition of AVH in schizophrenia is misleading and exerts negative consequences on the clinical work and empirical research.

Disorder of Selfhood in Schizophrenia: A Symptom or a Gestalt?

INTRODUCTION: The concept of schizophrenia (SCZ) was originally associated with a disorder of formal strata of the self. During the last two decades, empirical studies have demonstrated a selective hyper-aggregation of self-disorders in the SCZ spectrum. As with other scientific research areas, the role of self-disturbances in SCZ has been up for debate in various disciplines including cognitive sciences, philosophy of mind, and psychopathology. Several philosophical papers have used the psychopathological phenomena of "thought insertion" as an alleged example of a complete loss of minimal selfhood. In the field of psychopathology, it has been claimed that self-disorders may comprise a transdiagnostic phenotype. Common to these approaches is the underlying assumption that self-disorders reflect well-delineated and isolated symptoms akin to the notion of symptom in the medical model. The aim of this paper was to argue that the clinical manifestation of self-disturbances is to be seen as aspects of a Gestalt of disturbed experiential selfhood. METHODS: Seven videotaped interviews of patients with SCZ who were emblematic of very diverse symptomatological constellations were selected and jointly watched and discussed by the authors, who reached a consensus assessment. The interviews were semi-structured and narrative in nature in order to obtain faithful self-descriptions according to the standards of phenomenologically oriented interviews. For the purpose of this article, we chose 4 videos from which excerpts were verbatim transcribed and translated from Danish into English. RESULTS: The patients describe unique combinations of various psychopathological phenomena such as diminished sense of embodied self-presence, loss of ego boundaries, diminished sense of self, alienation and objectification of the experiential processes, mirror-phenomena, and Schneiderian passivity phenomena. DISCUSSION: Through an interweaving of the four vignettes and their subsequent psychopathological discussions, we argue that the invariant commonality across the different symptomatic expressions in these patients resides in a Gestalt of pervasive disturbance of self-experience. From a phenomenological perspective, these self-disturbances target a basic structure of phenomenal consciousness, namely, the first-person givenness of experience. We conclude that self-disorders reflect a trait-instability in the most basic structures of consciousness in SCZ and that its clinical manifestations are to be seen as aspects of a particular Gestalt rather than appearing as separate and well-delineated symptoms.

What is obsession? Differentiating obsessive-compulsive disorder and the schizophrenia spectrum.

Obsessive-compulsive symptoms are frequent in schizophrenia-spectrum disorders and often cause differential diagnostic challenges, especially in first-contact patients. Drawing upon phenomenology of cognition, we critically review classic and contemporary psychopathological notions of obsessive-compulsive phenomena and discuss their relevance for differential diagnosis between obsessive-compulsive disorder (OCD) and schizophrenia-spectrum disorders. The classic psychopathological literature defines true obsession as intrusions with intact resistance and insight and regards these features as essential to the diagnosis of OCD. In schizophrenia, the classic literature describes pseudo-obsessive-compulsive phenomena characterized by lack of resistance and an affinity with other symptoms such as thought disorder and catatonia. By contrast, the notions of obsession and compulsion are broader and conceptually vague in current diagnostic systems and research instruments. Here, these phenomena overlap with delusions as well as various subjective and behavioral anomalies, which we discuss in detail. Furthermore, we examine a link between obsessive-compulsive phenomena and disturbances of basic structures of experience in schizophrenia-spectrum disorders addressed in contemporary psychopathological research. We suggest that these experiential alterations have relevance for differential diagnosis and early detection in this complex symptom domain.

Relating self-disorders to neurocognitive and psychopathological measures in first-episode schizophrenia.

AIM: The notion of a disturbed self as the core feature of schizophrenia dates back to the founding texts on the illness. Since the development of the psychometric tool for examination of anomalous self-experience (EASE), self-disorders have become accessible to empirical research. Empirical studies have shown that EASE measured self-disorders predict schizophrenia spectrum in prospective studies and consistently show a selective hyper aggregation of self-disorder in schizophrenia and schizotypal disorders. The aim of this study is to investigate the relationship between self-disorders cognitive deficits and symptoms in schizophrenia. METHODS: Thirty-five non-acute first-episode patients with schizophrenia and 35 matched healthy controls were evaluated with EASE, cognitive deficits, and symptoms (PANSS positive, negative and general). [Correction added on 28 January 2022, after first online publication: the words, 'evaluated with' were missing and have now been added to the preceding sentence.] RESULTS: The results show that self-disorders and symptoms are correlated among patients with schizophrenia, but not with cognitive deficits. Moreover, with the exception of attentional deficits, neurocognitive impairment was not significantly higher among patients with schizophrenia compared to healthy controls. CONCLUSIONS: We argue that this adds support to a view of schizophrenia as being characterized by specific traits of pre-reflective self-disturbance, which are related to the severity of symptoms, whereas neurocognitive impairment reflects a separate or distinct aspect of schizophrenia.

"Transition" to Schizophrenia or Fluctuations within the Same Disorder?

BACKGROUND: To prevent or delay the onset of psychotic disorders or ameliorate their course, prodromal research has strived to identify and treat individuals at risk of developing psychosis. While this approach is laudable, it is, however, not entirely unproblematic from clinical and conceptual perspectives. For example, it remains unclear how we are to understand the development from a nonpsychotic, distressing condition such as schizotypal disorder to a psychotic disorder such as schizophrenia? The current terminology on the subject implies either a nonlinear jump ("conversion") or a more linear progression ("transition") from one disorder to another. To enrich our understanding of such diagnostic shifts, we examined the psychopathological pictures of patients who "transitioned" from schizotypal disorder to schizophrenia. METHODS: From a larger study on psychopathology, we examined 40 patients who were diagnosed with schizotypal disorder at baseline. At 5-year follow-up, 30 patients maintained the diagnosis of schizotypal disorder, while 10 were re-diagnosed with schizophrenia. We examined detailed descriptions of the 10 patients who progressed to schizophrenia, comparing psychopathology and level of functioning. RESULTS: The level of functioning decreased slightly from baseline to follow-up in 9 out of 10 patients. Eight patients had previously had micro-psychotic or psychotic experiences. All patients had self-disorders at baseline, and several patients had perceptual disorders. Nine patients had formal thought disorders at baseline. The progression is illustrated by 2 cases. CONCLUSION: In this small study, we did not find any striking changes in any of the patients, neither in terms of psychopathological manifestations nor in terms of their level of functioning. Thus, rather than witnessing a genuine "conversion" or "transition" from schizotypal disorder to schizophrenia, we observed dimensional fluctuations within the same condition.

Disordered Selfhood in Schizophrenia and the Examination of Anomalous Self-Experience: Accumulated Evidence and Experience.

Disordered selfhood in schizophrenia was rediscovered at the turn of the millennium. In 2005, Psychopathology 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.

Formal Thought Disorder and Self-Disorder: An Empirical Study.

Background: Formal thought disorder was constitutively linked to the original concept of schizophrenia and has since been one of central features supporting its diagnosis. Bleuler considered formal thought disorder as a fundamental symptom of schizophrenia among other fundamental symptoms, including ego disorders. The contemporary concept of self-disorder represents a more developed, nuanced, and systematic approach to disturbances of self-experience than the Bleulerian concept of ego disorders. As fundamental symptoms, on Bleuler's account, are persistently present in every case, an association between these symptoms could be expected. The purpose of this study was to examine the association between self-disorder and formal thought disorder. Methods: A sample of 94 diagnostically heterogeneous patients was examined for formal thought disorder using clinical rating and a proverb test. The proverb test was analyzed for two different aspects of formal thought disorder: literal responses and bizarre responses. The sample was comprehensively assessed for psychopathology, including self-disorder as measured with the Examination of Anomalous Self-Experience scale. Results: The patients, who provided bizarre responses, had a higher level of self-disorder, more negative symptoms, lower level of social functioning, and lower level of intelligence. Bizarre answers aggregated in patients diagnosed within the schizophrenia spectrum compared with patients outside the schizophrenia spectrum. We found moderate correlations between the two measures of formal thought disorder (clinically rated and bizarre responses) and self-disorder (0.454 [p < 0.01] and 0.328 [p < 0.01]). Literal responses did not differ between diagnostic groups and also did not correlate with bizarre responses. Specificity of bizarre responses for a diagnosis within schizophrenia spectrum was 86.89%, whereas sensitivity was 40.85%. Conclusion: The close relation between formal thought disorder and self-disorder further adds to the notion of self-disorder as a unifying psychopathological core beneath the apparently heterogeneous symptoms of schizophrenia.

The Self in the Spectrum: A Meta-analysis of the Evidence Linking Basic Self-Disorders and Schizophrenia.

Disturbed self-experience has been reported as a characteristic feature of schizophrenia since the first formulation of its diagnostic concept; however, only in the last 2 decades an explicit notion of basic Self-disturbance, or Self-Disorders (SD), has emerged as target for a systematic research program. We conducted systematic searches in bibliographical databases to identify cross-sectional studies that explored SD across different diagnostic groups and explored diagnostic ascription within or outside schizophrenia spectrum disorders (SSD) as main outcome. Data were pooled using fixed- and random-effects meta-analysis models. Heterogeneity was assessed using stratified meta-analyses and meta-regression. Of 218 identified studies, 32 were included in the systematic review and 27 in the meta-analysis. Patients diagnosed with SSD scored higher on measures of SD than healthy controls (HC) (Hedges' g = 1.8; 95% CI = 1.5 to 2.0), individuals diagnosed with other mental illness (OMI) (1.9; 1.6 to 2.2), bipolar or affective disorders (1.8; 1.4 to 2.2), and clinical high risk for psychosis (CHR) (1.6; 0.9 to 2.4). Patients with schizotypy or schizotypal personality disorder scored higher on measures of SD than OMI (1.5; 1.3 to 1.8) and HC (1.4; 1.1 to 1.7). Patients with first-episode psychosis scored higher on measures of SD than HC (2.5; 2.1 to 2.9) and OMI (1.6; 1.2 to 2.1). Subjects at CHR scored higher on measures of SD than HC (2.0; 1.7 to 2.2) and OMI (19; 1.6 to 2.2). Overall, heterogeneity ranged from negligible to high, especially in comparisons of the target group with OMI, probably as a reflection of the immanent diagnostic heterogeneity of this group. The findings suggest that SD selectively aggregate within schizophrenia spectrum disorders as compared to other mental disorders and that they could be a central phenotypic marker of vulnerability to schizophrenia across the different shades of severity of its spectrum of disorders.