Somatosensory Processing and Schizophrenia Liability: Proprioception, Exteroceptive Sensitivity, and Graphesthesia Performance in the Biological Relatives of Schizophrenia Patients.

In the present study, the authors examined somatosensory processing in 30 biological relatives of persons with schizophrenia (hereafter called "schizophrenia relatives"), 30 biological relatives of persons with bipolar affective disorder (psychiatric family control subjects), and 30 healthy control subjects with no family history of psychopathology. All 3 groups completed a weight discrimination task, a 2-point discrimination task, and a complex cognitive somatosensory task (i.e., graphesthesia). The schizophrenia relatives performed significantly worse on all 3 somatosensory tasks compared with both the healthy control subjects and the bipolar relatives. The healthy control subjects and psychiatric family control subjects showed no significant differences on any of the somatosensory tasks. Within the weight discrimination and 2-point discrimination tasks, schizophrenia relatives showed group differences on the d' index, the measure of sensitivity, whereas all 3 groups did not differ on lnβ, the measure of response bias, suggesting a genuine difference in weight and touch sensitivity. The d' value of the weight discrimination task was significantly associated with both the cognitive-perceptual factor and negative symptom factor of the clinical questionnaire (e.g., Schizotypal Personality Questionnaire; SPQ), whereas the 2-point discrimination d' value and graphesthesia scores were significantly associated only with the cognitive-perceptual factor of the SPQ. Implications for the possible relation between somatosensory task performance and schizophrenia liability are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Consideration of the Challenges, Complications, and Pitfalls of Taxometric Analysis.

The taxometric analytic procedures developed by P. E. Meehl and colleagues represent powerful statistical tools for use in the evaluation of observed quantitative data for the possible existence of a qualitative latent class, natural subgroup, or, more commonly, a taxon. Taxometric methods, like any other statistical procedures, require thoughtful application, and the responsibility for proper interpretation of the results from a taxometric study lies with the investigator. Any investigator using taxometric methods must be mindful of those substantive and methodological issues that will facilitate the most fruitful utilization of the general taxometric approach, as well as those issues that will handicap or, perhaps, fatally flaw a taxometric investigation. A number of these issues are highlighted and discussed in this article, and a reader's, writer's, and reviewer's guide for the evaluation of taxometric research reports is provided. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Confirming the latent structure and base rate of schizotypy: A taxometric analysis.

P. E. Meehl's (1962, 1990) model of schizotypy and the development of schizophrenia implies that the structure of liability for schizophrenia is dichotomous and that a "schizogene" determines membership in a latent class, or taxon (Meehl and R. R. Golden, 1982). The authors sought to determine the latent structure and base rate of schizotypy. They applied Meehl's (1973) MAXCOV-HITMAX taxometric analytic procedures to a subset of items from the Perceptual Aberration Scale (PAS; L. J. Chapman et al, 1978), a prominent psychometric index of schizotypy, derived from a randomly ascertained nonclinical sample (N?=?1,093). The results, in accordance with Meehl's conjectures, strongly suggest that schizotypy, as assessed by the PAS, is taxonic at the latent level with a general population taxon base rate of approximately .10. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Assessment of premorbid social competence in schizophrenia: A methodological note.

The developmental theory underlying the Zigler-Phillips Social Competence Scale ({ZPSCS}; Zigler & Phillips, 1961) has important implications for using the scale to assess premorbid adjustment in schizophrenia. Many studies using the {ZPSCS} have scored the scale in an inconsistent manner or have not clearly limited the premorbid period to that prior to the onset of illness. {ZPSCS} ratings of social competence change over time, therefore studies using the {ZPSCS} should attend closely to the definition of the premorbid period and indicate whether premorbid or current adult social competence is being assessed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Schizotypy and sustained attention: Confirming evidence from an adult community sample.

Sustained attention deficits represent one of the most robust findings in the study of schizophrenia and schizotypy. However, very little is known about the nature of sustained attention performance and schizotypy in the general adult population. The present study assessed sustained attention performance in a large, normative adult community sample (N = 305) with no history of psychosis using the Continuous Performance Test-identical pairs version (CPT-IP). Associations between overall CPT-IP performance and schizotypal personality disorder features, controlling for the effects of age, sex, and educational level, revealed diminished sensitivity (d', discriminability), and increased random errors were related to increased reality distortion features. These data, drawn from a general population sample, provided support for overall sustained attention deficits as an endophenotype for schizophrenia liability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Models of positive and negative symptoms in schizophrenia: An empirical evaluation of latent structures.

The present investigation empirically evaluated three competing models of the relations between positive and negative symptoms in schizophrenia, namely the I. I. Gottesman et al (see record 2005-09771-003), N. C. Andreasen and S. Olsen's (see record 1982-30452-001), and T. J. Crow's (see record 1981-28160-001) severity-liability model unidimensional bipolar model, independent dual-process model. Using positive and negative symptom ratings based on 220 schizophrenic subjects, the results of a LISREL VI confirmatory factor analysis revealed that Crow's model of positive and negative symptoms provided the best fit to the observed data among the 3 models. The severity-liability model provided a modest fit to observed data, and Andreasen's model fit the data poorly. Results support the validity of the positive and negative symptom distinction in schizophrenia and as providing substantive empirical support for Crow's independent dual-process model. The methodological advantages of confirmatory factor analysis in the specification and evaluation of theoretical models in experimental and developmental psychopathology are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Resolving the latent structure of schizophrenia endophenotypes using expectation-maximization-based finite mixture modeling.

Prior research has focused on the latent structure of endophenotypic markers of schizophrenia liability, or schizotypy. The work supports the existence of 2 relatively distinct latent classes and derives largely from the taxometric analysis of psychometric values. The present study used finite mixture modeling as a technique for discerning latent structure and the laboratory-measured endophenotypes of sustained attention deficits and eye-tracking dysfunction as endophenotype indexes. In a large adult community sample (N=311), finite mixture analysis of the sustained attention index d′ and 2 eye-tracking indexes (gain and catch-up saccade rate) revealed evidence for 2 latent components. A putative schizotypy class accounted for 27% of the sample. A supplementary maximum covariance taxometric analysis yielded highly consistent results. Subjects in the schizotypy component displayed higher rates of schizotypal personality features and an increased rate of treated schizophrenia in their 1st-degree biological relatives compared with subjects in the other component. Implications of these results are examined in light of major theories of schizophrenia liability, and methodological advantages of finite mixture modeling for psychopathology research, with particular emphasis on genomic issues, are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Schizotaxia, schizotypy, and schizophrenia: Paul E. Meehl's blueprint for the experimental psychopathology and genetics of schizophrenia.

Paul E. Meehl proposed a model of the cause and pathogenesis of schizophrenia and related states in the early 1960s (Meehl, 1962), which he later revised in 1990 (Meehl, 1990). His model emphasized a genetically influenced aberration in neural transmission that could eventuate in clinical schizophrenia, nonpsychotic schizotypic states, or apparent normalcy depending on the coexistence of other factors. His model embodied the core ideas of the diathesis-stressor framework that would come to dominate experimental and developmental psychopathology for the next 40 years. The author reviews Meehl's model of schizotaxia, schizotypy, and schizophrenia and reviews and clarifies some frequent misunderstandings of the model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Thought disorder, perceptual aberrations, and schizotypy.

Empirical links between schizophrenia and schizotypic psychopathology were examined. The Perceptual Aberration Scale (PerAb; L. J. Chapman, J. O. Chapman, & M. L. Raulin; see record 1979-23733-001) was used to identify putative schizotypic individuals and a contrast group of nonschizotypic controls. The Thought Disorder Index (TDI; M. J. Coleman et al.; see record 1994-15942-001) was used to quantify and classify thought disorder in these individuals. High PerAb participants, selected for having an increased number of self-reported perceptual and body image aberrations, showed an elevation in the amount and frequency of thought disorder as well as an increased number of idiosyncratic verbalizations. This supports the hypothesis that psychometrically identified schizotypic individuals display thought disorder similar to that shown by schizophrenic patients and some of their 1st-degree relatives, suggesting that there is a relation between schizotypic psychopathology, as tapped by the PerAb scale, and clinical schizophrenia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Psychosis proneness and clinical psychopathology: Examination of the correlates of schizotypy.

The present report examined the associations between the Perceptual Aberration Scale (PAS), a prominent psychometric index of hypothetical psychosis proneness, and several measures of clinical psychopathology in a nonpsychotic psychiatric sample (N?=?101). Patients were examined by experienced clinicians using structured psychiatric interviews to assess Diagnostic and Statistical Manual of Mental Disorders-III—Revised (DSM-III—R) Axis I and II conditions and rated for anxiety, depression, severity of illness, and current adult social competence. Elevated scores on the PAS were most closely associated with anxiety and depression as well as schizotypal, schizoid, avoidant, and obsessive–compulsive personality disorder symptomatology. Hierarchical regression analysis identified schizotypal symptoms and anxiety as the two underlying psychopathological processes most useful in explaining variance in PAS scores. Results are interpreted as supporting both the clinical relevance and research utility of the PAS and enhancing the construct validity of Meehl's model of schizotypy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)