Finding the "genuine" schizotype: a model and method for resolving heterogeneity in performance on laboratory measures in experimental psychopathology research

Schizotypy

Schizophrenia is the most devastating form of psychopathology known to humankind, and it has been slow to yield clues to its origins. Meehl's (1962 , 1990 ) model detailed the nature of the latent liability for schizophrenia known as schizotypy and provided a major organizing function for research on schizophrenia. The schizotypy model integrates genetic and environmental contributions to liability as well as accounting for a range of clinical outcomes, all deriving from a genuine liability for the illness. Schizotypy, as a latent personality organization that harbors the liability for schizophrenia, provides a framework for detecting fundamental features of liability to schizophrenia prior to the onset of clinical illness. The schizotypy model is reviewed, the strategic benefits of it are discussed, and methods for detecting schizotypy are presented. A focus on perceptual aberrations—a schizotypic feature—in individuals unaffected by schizophrenia has yielded valuable clues to preclinical disturbances in neurocognitive processes, risk for schizophrenia among biological relatives, and genomic substrates, all of which are of interest to schizophrenia researchers.

A hierarchical finite mixture model that accommodates zero-inflated counts, non-independence, and heterogeneity

A number of mixture modeling approaches assume both normality and independent observations. However, these two assumptions are at odds with the reality of many data sets, which are often characterized by an abundance of zero-valued or highly skewed observations as well as observations from biologically related (i.e., non-independent) subjects. We present here a finite mixture model with a zero-inflated Poisson regression component that may be applied to both types of data. This flexible approach allows the use of covariates to model both the Poisson mean and rate of zero inflation and can incorporate random effects to accommodate non-independent observations. We demonstrate the utility of this approach by applying these models to a candidate endophenotype for schizophrenia, but the same methods are applicable to other types of data characterized by zero inflation and non-independence.

An Overview of the Association between Schizotypy and Dopamine

Schizotypy refers to a constellation of personality traits that are believed to mirror the subclinical expression of schizophrenia in the general population. Evidence from pharmacological studies indicates that dopamine (DA) is involved in the etiology of schizophrenia. Based on the assumption of a continuum between schizophrenia and schizotypy, researchers have begun investigating the association between DA and schizotypy using a wide range of methods. In this article, we review published studies on this association from the following areas of work: (1) experimental investigations of the interactive effects of dopaminergic challenges and schizotypy on cognition, motor control, and behavior (2), dopaminergically supported cognitive functions (3), studies of associations between schizotypy and polymorphisms in genes involved in dopaminergic neurotransmission, and (4) molecular imaging studies of the association between schizotypy and markers of the DA system. Together, data from these lines of evidence suggest that DA is important to the expression and experience of schizotypy and associated behavioral biases. An important observation is that the experimental designs, methods, and manipulations used in this research are highly heterogeneous. Future studies are required to replicate individual observations, to enlighten the link between DA and different schizotypy dimensions (positive, negative, cognitive disorganization), and to guide the search for solid DA-sensitive behavioral markers. Such studies are important in order to clarify inconsistencies between studies. More work is also needed to identify differences between dopaminergic alterations in schizotypy compared to the dysfunctions observed in schizophrenia.

Current status of the scientific study of the personality disorders: an overview of epidemiological, longitudinal, experimental psychopathology, and neurobehavioral perspectives

Research on the nature and development of personality disorders has grown immensely over the past thirty years. A selective summary overview is given of the current status of the scientific study of the personality disorders from several perspectives, including the epidemiological, longitudinal, experimental psychopathology, and neurobehavioral perspectives. From this research, we now know that approximately 10 percent of the general population suffer from a diagnosable personality disorder. Moreover, contrary to nearly a century of theory and clinical pedagogy, modern longitudinal studies clearly suggest that personality disorders decrease in severity over time. The mechanisms by which this change occurs are not understood at present, though it is not likely that change in underlying normal personality systems drives the change in personality disorder. The methods of the experimental psychopathology laboratory, including neuroimaging approaches, are being brought to bear on the nature of personality disorders in efforts to relate neurobiological and neurocognitive functions to personality disorder symptomatology. A model that links personality disorder feature development to underlying, interacting brain-based neurobehavioral systems is reviewed in brief. Current issues and findings illustrative of these developments are given using borderline personality disorder as an exemplar. Finally, areas of intersection between psychoanalytic treatment approaches and the growing science of personality disorder are highlighted.

The schizotypal ambivalence scale as a marker of schizotypy

The present study examined the psychometric properties of the Schizotypal Ambivalence Scale (SAS) in a sample of 1798 young adults. The study also investigated the concurrent validity of the measure for identifying schizophrenic-like symptoms in a sample of 43 high scorers on the scale and 43 control participants. Previous findings indicated that high scores on the SAS were associated with schizophrenia-spectrum pathology in a sample of schizotypic young adults selected with other measures. However, this is the first study to assess schizophrenic-like psychopathology in a sample selected using the SAS. The SAS has good internal consistency (coefficient alpha = 0.84) and test-retest reliability (intraclass correlation = 0.74 across 9 weeks). As hypothesized, the ambivalence group exceeded the control group on interview ratings of schizotypal, schizoid, paranoid, psychotic-like, and negative symptoms, as well as exhibiting poorer overall functioning. The SAS seems to be a promising measure of schizotypy in young adults.

[The empirical development of transference-focused psychotherapy]

The author describes the stages of elaboration of Transference Focused Psychotherapy (TFP) : choice of theoretical model, observation and analyses of several sessions of psychotherapy led by experienced therapists, team discussions on problems encountered that rise both from the pathology itself and from the therapeutic approach applied, a quest of empirical data to explain as much the personality disorder as its neurological and psychological roots, etc. The author reviews the efforts made to arrive at the description in writing of a manual on TFP, a manual that meets the criteria of a treatment method. Finally, the author summarizes studies conducted to measure the psychotherapeutic efficacy of the method and the possibilities of generalizability.

Schizotypy and individual differences in the frequency of normal associations in verbal utterances

BACKGROUND

Recent empirical evidence [Maher, B.A., Manschreck, T.C., Linnert, J., Candela, S., 2005. Quantitative assessment of the frequency of normal associations in the utterances of schizophrenia patients and healthy controls. Schizophrenia Research 78, 219-224] shows that schizophrenia patients produce an elevated rate of normative thought associations in verbal utterances as measured by an objective computerized procedure. An important theoretical question concerns whether such an elevated rate of associative activity is due merely to psychosis, or can it be found in schizotypic subjects with no prior history of psychosis.

METHODS

We hypothesized that schizotypic features should be correlated with associative performance, especially the positive symptom-like schizotypic features. The present study examined associative performance in psychometrically-identified schizotypic subjects (n=25) and normal control (n=29) subjects. We studied individual differences in schizotypal personality features in relation to the associative performance index.

RESULTS

Level of normative associations was correlated with total schizotypic features, particularly those involving reality distortion and disorganization. Regression analysis revealed higher levels of disorganization features and lower levels of negative schizotypal features uniquely accounted for variation in the associative performance index. Partial correlation analysis suggested that the negative schizotypic features dimension may function as a suppressor variable moderating the relationship between disorganization and level of normative associations.

CONCLUSIONS

Disorganization-related schizotypal features among individuals with no prior history of psychosis are correlated with elevated levels of normative associations. This relationship is most likely moderated by negative schizotypic features. These data support the presence of hyperassociative processes in those deemed to be at elevated risk for schizophrenia (or, more broadly perhaps, psychosis). Our findings support the utility of measuring associative performance using an objective measure and suggest that associative performance may be an endophenotype [Gottesman, I., Gould, T., 2003. The endophenotype concept in psychiatry: etymology and strategic intentions. American Journal of Psychiatry 160, 636-645] for schizophrenia.

Sustained attention deficits in relation to psychometrically identified schizotypy: evaluating a potential endophenotypic marker

Sustained attention deficits have been posited as a potential endophenotypic marker of vulnerability to schizophrenia. Prior studies have indicated that schizophrenia patients, their first-degree relatives, and psychosis-prone individuals, identified on the basis of measures of positive schizotypy, have demonstrated sustained attention deficits. To date, there have been no published reports of sustained attention deficits in individuals with negative schizotypy, as measured by the revised Social Anhedonia Scale. In this study, we examined sustained attention, measured with the CPT-Identical Pairs version, in 160 individuals with elevated scores on the Chapman Perceptual Aberration and/or Magical Ideation Scales, 96 individuals with elevated scales on the Social Anhedonia Scale, and 137 controls. Both psychosis-prone groups performed more poorly than the controls in terms of discrimination ability, as measured by d', though the groups did not differ in terms of either their reaction time or overall response criterion (lnbeta). These results provide evidence that both positive and negative aspects of schizotypy are associated with sustained attention deficits, as measured by the Continuous Performance Test. The findings add to the converging evidence indicating that sustained attention deficits are a potential endophenotypic indicator of a schizophrenia diathesis.