Schizotypy and Etiology of Schizophrenia Spectrum Disorders
Schizotypy and Etiology of Schizophrenia Spectrum Disorders
Schizotypy provides a useful construct for understanding the development of schizophrenia spectrum disorders. As research on the epidemiology of psychotic symptoms and clinical risk for psychosis has expanded, conceptual challenges have emerged to comprehend the nature and borders of the space comprised between personality variation and psychosis. Schizotypy is considered in light of these more recent constructs. It is suggested that rather than being superseded by them due to their higher specificity and predictive power for transition to psychosis, schizotypy integrates them as it constitutes a dynamic continuum ranging from personality to psychosis. The advantages of schizotypy for studying schizophrenia etiology are discussed (eg, it facilitates a developmental approach and the identification of causal, resilience, and compensating factors and offers a multidimensional structure that captures etiological heterogeneity). An overview of putative genetic, biological, and psychosocial risk factors is presented, focusing on communalities and differences between schizotypy and schizophrenia spectrum disorders. The found notable overlap supports etiological continuity, and, simultaneously, differential findings appear that are critical to understanding resilience to schizophrenia. For example, discrepant findings in genetic studies might be interpreted as suggestive of sets of independent genetic factors playing a differential role in schizotypy and schizophrenia: some would influence variation specifically on schizotypy dimensions (ie, high vs low schizotypy, thereby increasing proneness to psychosis), some would confer unspecific liability to disease by impacting neural properties and susceptibility to environmental factors (ie, high vs low resilience to disorder) and some might contribute to disease–specific characteristics. Finally, schizotypy's promise for studying gene-environment interactions is considered.
Schizotypy was introduced to represent the inherited vulnerability to schizophrenia spectrum disorders expressed as a multidimensional personality organization. The interaction of this vulnerability substrate with other genetic and environmental factors shapes the risk of presenting spectrum disorders and yields a wide range of phenotypic variance. Schizotypy is associated with heightened risk for the development of psychotic disorders, although most schizotypes are not expected to develop psychosis, and constitutes a useful framework to study etiological factors of schizophrenia spectrum disorders. Assessment of schizotypy provides an entry point for identifying individuals possessing liability to psychosis prior to the appearance of clinical manifestations. This should facilitate the study of developmental pathways to psychosis and the identification of protective factors in individuals not presenting with typical confounding factors associated with schizophrenia spectrum disorders.
The construct of schizotypy was developed both within the individual differences and medical traditions, which has led to differences in its conceptualization. The fully dimensional model of schizotypy, rooted in personality tradition, proposes schizotypy as part of normal personality, being a source of both healthy variation and predisposition to psychosis. This model encompasses the more restrictive conceptualization derived from the medical tradition that dimensionality in psychosis exists but is restricted to the severity of presentation (from personality pathology to the most extreme form of schizophrenia), viewing schizotypy as a forme fruste of psychosis (quasi-dimensional model). These models involve different views on the usefulness of schizotypy for studying schizophrenia spectrum disorders. The medical perspective tends to view schizotypy as a risk factor and a link in the chain towards schizophrenia. The reference point is the pathological, and the relevant focus is understanding the transition from subclinical stages to psychosis. From this perspective, studying nonclinical variation is not highly informative, and this has hindered integration of knowledge derived from the individual differences and clinical fields. This has also slowed down the adoption of a developmental psychopathology perspective in the field of psychosis (which recognizes continuity between normal and abnormal and puts the emphasis in the study of interindividual differences and processes contrary to traditional disease models of causation), even if a number of researchers pioneered a developmental conceptualization of schizophrenia in the early 90's. In other psychopathology domains, more fruitful research has been conducted to understand connections between personality and psychopathology. This possibly relates to challenges posed by the larger phenotypic discontinuity existing between trait and disorder in the case of psychosis compared with other domains, say trait anxiety and anxiety disorders, the failure of radical "Eysenckian dimensionalism" to recognize that there is a transition between healthy schizotypy personality and psychotic illness states (not meaning that they are unconnected), and that schizotypy presents more challenges than other personality dimensions (eg, definition of the low end of schizotypy).
This article focuses on how schizotypy can be informative for studying schizophrenia spectrum disorders. It first addresses currently unresolved conceptual issues regarding schizotypy and then offers a brief overview on candidate causal factors regarding commonalities and differences between schizotypy and schizophrenia spectrum disorders.
Abstract and Introduction
Abstract
Schizotypy provides a useful construct for understanding the development of schizophrenia spectrum disorders. As research on the epidemiology of psychotic symptoms and clinical risk for psychosis has expanded, conceptual challenges have emerged to comprehend the nature and borders of the space comprised between personality variation and psychosis. Schizotypy is considered in light of these more recent constructs. It is suggested that rather than being superseded by them due to their higher specificity and predictive power for transition to psychosis, schizotypy integrates them as it constitutes a dynamic continuum ranging from personality to psychosis. The advantages of schizotypy for studying schizophrenia etiology are discussed (eg, it facilitates a developmental approach and the identification of causal, resilience, and compensating factors and offers a multidimensional structure that captures etiological heterogeneity). An overview of putative genetic, biological, and psychosocial risk factors is presented, focusing on communalities and differences between schizotypy and schizophrenia spectrum disorders. The found notable overlap supports etiological continuity, and, simultaneously, differential findings appear that are critical to understanding resilience to schizophrenia. For example, discrepant findings in genetic studies might be interpreted as suggestive of sets of independent genetic factors playing a differential role in schizotypy and schizophrenia: some would influence variation specifically on schizotypy dimensions (ie, high vs low schizotypy, thereby increasing proneness to psychosis), some would confer unspecific liability to disease by impacting neural properties and susceptibility to environmental factors (ie, high vs low resilience to disorder) and some might contribute to disease–specific characteristics. Finally, schizotypy's promise for studying gene-environment interactions is considered.
Introduction
Schizotypy was introduced to represent the inherited vulnerability to schizophrenia spectrum disorders expressed as a multidimensional personality organization. The interaction of this vulnerability substrate with other genetic and environmental factors shapes the risk of presenting spectrum disorders and yields a wide range of phenotypic variance. Schizotypy is associated with heightened risk for the development of psychotic disorders, although most schizotypes are not expected to develop psychosis, and constitutes a useful framework to study etiological factors of schizophrenia spectrum disorders. Assessment of schizotypy provides an entry point for identifying individuals possessing liability to psychosis prior to the appearance of clinical manifestations. This should facilitate the study of developmental pathways to psychosis and the identification of protective factors in individuals not presenting with typical confounding factors associated with schizophrenia spectrum disorders.
The construct of schizotypy was developed both within the individual differences and medical traditions, which has led to differences in its conceptualization. The fully dimensional model of schizotypy, rooted in personality tradition, proposes schizotypy as part of normal personality, being a source of both healthy variation and predisposition to psychosis. This model encompasses the more restrictive conceptualization derived from the medical tradition that dimensionality in psychosis exists but is restricted to the severity of presentation (from personality pathology to the most extreme form of schizophrenia), viewing schizotypy as a forme fruste of psychosis (quasi-dimensional model). These models involve different views on the usefulness of schizotypy for studying schizophrenia spectrum disorders. The medical perspective tends to view schizotypy as a risk factor and a link in the chain towards schizophrenia. The reference point is the pathological, and the relevant focus is understanding the transition from subclinical stages to psychosis. From this perspective, studying nonclinical variation is not highly informative, and this has hindered integration of knowledge derived from the individual differences and clinical fields. This has also slowed down the adoption of a developmental psychopathology perspective in the field of psychosis (which recognizes continuity between normal and abnormal and puts the emphasis in the study of interindividual differences and processes contrary to traditional disease models of causation), even if a number of researchers pioneered a developmental conceptualization of schizophrenia in the early 90's. In other psychopathology domains, more fruitful research has been conducted to understand connections between personality and psychopathology. This possibly relates to challenges posed by the larger phenotypic discontinuity existing between trait and disorder in the case of psychosis compared with other domains, say trait anxiety and anxiety disorders, the failure of radical "Eysenckian dimensionalism" to recognize that there is a transition between healthy schizotypy personality and psychotic illness states (not meaning that they are unconnected), and that schizotypy presents more challenges than other personality dimensions (eg, definition of the low end of schizotypy).
This article focuses on how schizotypy can be informative for studying schizophrenia spectrum disorders. It first addresses currently unresolved conceptual issues regarding schizotypy and then offers a brief overview on candidate causal factors regarding commonalities and differences between schizotypy and schizophrenia spectrum disorders.
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