Background: The human genome project has affirmed the importance of non-genetic factors in human development. Attachment style is considered to be a diathesis for psychopathology and an important determinant regarding interpersonal functioning. Epidemiological research has indicated that there is significant aetiological continuity between symptoms of schizotypy and clinical symptoms of schizophrenia. Limited research has investigated the association between attachment and schizotypy. Aim: To investigate the predictive association between schizotypy and attachment styles, interpersonal functioning and depression within a stress-diathesis model of schizophrenia. Design and Methodology: A quantitative cross-sectional within group design using a clinical sample was employed. Hierarchical linear regressions and path models were computed to investigate the hypothesised predictive association between the variables. Main finding: The best predictor of schizotypy is understood in the context of an interaction between developmental vulnerability factors (attachment styles) and current stressors (level of interpersonal functioning). Depression mediated the impact of interpersonal functioning on schizotypy but was not a significant solo predictor of schizotypy. Discussion: The potential implications of the findings are discussed in regard to a dimensional stress diathesis model of schizophrenia. The robustness of the research design employed is discussed and suggestions for future research made.

Indiana University-Purdue University Indianapolis (IUPUI) / Schizophrenia is a complex and debilitating mental disorder characterized by a myriad of symptoms that affect multiple aspects of functioning. Metacognition, or the ability to form complex notions of oneself and others, has been evidenced to be deficient in schizophrenia. As such, one burgeoning line of research has sought to elucidate the role of metacognitive capacity on functional outcome across the schizophrenia spectrum. Although there is a substantial body of evidence about the role of metacognition in clinical manifestations of the disorder, few studies to date have explored whether similar deficits can be seen in individuals at risk for schizophrenia. One such at risk group is that of schizotypy wherein individuals demonstrate attenuated trait-like characteristics resembling less severe versions of those seen in psychosis. The aim of the current study was to investigate metacognitive capacities in this group. To that end, 67 participants were recruited (schizotypy = 34, control = 33) and two primary hypotheses were developed: 1) Individuals with schizotypy will exhibit significantly worse metacognition than a non-schizotypy group; and 2) Metacognition will account for additional variance above and beyond social cognition in predicting social functioning. Contrary to our hypotheses, group differences a metacognition and its subdomains were not significant. Further, inconsistent with studies in chronic schizophrenia, metacognition did not significantly predict social functioning. Our findings suggest that metacognition is preserved in schizotypy.

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In the general population, psychosis-like experiences have been extensively studied under the psychometric rubric of schizotypy (psychosis-proneness). As such, Phase 1 of this thesis aimed to assess the distribution of schizotypal traits and associated personality correlates displayed within a quota sample of the general population stratified by Gender and Ageband, the emphasis being upon anomalous experiences (positive schizotypy). Respondents (N = 130) completed a battery of established self-report measures assessing thirteen areas of personal experience. Correlational analysis revealed that eleven of the measures of ostensibly anomalous experiences possessed significant intercorrelations. Subsequent principal components analysis identified three factors accounting for 64.91% of the total variance; the factor accounting for the greatest proportion of variance (42.97%) was interpreted as representing a psychological disposition towards reporting ‘Anomalous Cognitions’. The other two factors are named ‘Lifeview System’ (12.60% of total variance) and ‘Social Adaptation Skills’ (9.34% of total variance). From the principal factor inclusion criteria for Phase 2 of the research are explicated. No significant mean Gender differences were revealed for the six self-report measures that provided unique contributions toward anomalous cognitions, the two self-report measures that uniquely contributed toward a lifeview system, or for the single self-report measure that uniquely contributed toward social adaptation skills. Additionally, four of the nine self-report measures which provided unique factorial contributions generated significant mean differences between Agebands, with a further three providing trends toward significant mean differences. Implications for the role of anomalous cognitions, a framework for a lifeview system, and social adaptation skills with regard to psychosis-proneness are discussed. From the primary factor (anomalous cognitions), three experimental groups were identified for cognitive testing: respondents scoring 1) ≤ 20th percentile; 2) 10% ± the mean; and 3) ≥ 80th percentile. This procedure provided a total of 78 participants (three x 26) for Phase 2 testing. Phase 2 of this thesis sought to identify some of the cognitive mechanisms underpinning subclinical anomalous cognitions with a view to deciphering which measures best predicted experimental group membership. A comprehensive literature review highlighted six domains of cognition, five accompanying self-report measures, and two measures of intelligence functioning (verbal and fluid/visuoconstructive), which, following previous research, were utilised as covariate measures. Based on prescribed delineation points, participants were allocated, according to scores on the primary factor from Phase 1, to one of three experimental groups (low-, mid, and high-anomalous cognitions). Of the six cognitive domains—1) sustained visual attention; 2) false (illusory) memory; 3) probability reasoning (decision making); 4) object recognition; 5) reality monitoring; and 6) self-monitoring—four succeeded in eliciting significant mean differences between experimental groups with the noted exceptions of sustained visual attention and self-monitoring. Subsequent canonical discriminant analyses identified that the best predictors of XPG membership were the number of critical lures recognised on the false memory test, the number of correct responses and confidence when uncertain on the object recognition test, plus two self-report measures pertaining to comorbid psychopathology and the vividness of visual imagery. In light of previous research, the inclusion of fasle (illusory) memory biases, the comorbidity of mental pathology (especially, depressive and anxiety-related symptoms), and the vividness of visual imagery are unsurprising; however, the two object recognition variables (the ‘number of correct responses’ and ‘confidence when uncertain’) offer exciting avenues for future research into the continuum of psychosis. Moreover, the ‘confidence when uncertain’ data from the object recognition test (perceptual) and the probability reasoning (decision making) data from the Beads test suggest that cognitive underconfidence may well be an enduring personality disposition in those reporting elevated levels of anomalous cognitions, including positive and disorganised schizotypal personality traits. The results of Phase 2 add confirmatory evidence to previous research suggestive of memory and perceptual biases plus comorbid psychopathology and the vividness of visual imagery as being integral to the psychogenesis of psychosis-like (anomalous) symptomatology.

A large body of research has demonstrated general relations of sleep complaints with psychological disorders, including anxiety, depression, and dissociation/schizotypy. In contrast, very few studies have focused on the specificity of sleep complaints to daytime symptoms. Identifying sleep disturbances that show evidence of specificity is important for differential diagnosis and assessment. This study used the structure of self-reported sleep complaints as a framework for examining specificity. Comprehensive questionnaire and interview measures of sleep disturbance were submitted to factor analyses in students and psychiatric patients. These analyses revealed the presence of three well defined higher order factors: Lassitude, Insomnia, and Unusual Sleep Experiences. These factors were then correlated with interview and questionnaire measures of daytime symptoms. Lassitude was specific to dysphoria, whereas Insomnia had weaker, nonspecific relations with daytime symptoms. Fatigue, a component of Lassitude, showed the strongest evidence of specificity. Unusual Sleep Experiences was specific to symptoms of posttraumatic stress disorder (PTSD) and dissociation. In particular, the Nightmares component of Unusual Sleep Experiences was strongly related to PTSD and the Sleep Hallucinations component of Unusual Sleep Experiences was strongly related to dissociation.

Introduction: Schizotypy is a personality trait that shares some of the characteristics of clinical disorders such as schizophrenia. Similarities are found in expression of psychotic-like experiences and presence of attenuated negative signs. Furthermore, schizotypal samples are associated with impairments in cognitive tasks, albeit in a less comprised form. For these reasons and others, schizotypy is considered a part of the extended-phenotype of schizophrenia and as such can be utilised as an analogue sample without some of theconfounds associated with illness. Objective: The aim of the PhD is to examine the relationship of schizotypal features and brain function and structure in a sample of adolescents and young adults (age 16-25 years). This will attempt to provide further evidence for the placement of schizotypy on the continuum, along with insights into pathophysiological mechanisms involved in schizophrenia and related disorders. Methods: The study involved three main phases: recruitment via an online survey, further neuropsychological testing and brain imaging on selected high schizotypes and controls. The thesis comprises 5 papers/experiments. Paper 1 utilises confirmatory factor analysis (CFA) to examine the factorial structure of the schizotypal personality questionnaire (SPQ) in a community sample aged 16-25 years. It also examined the effects of demographics on schizotypal levels. Paper 2 examined the association between schizotypy and measures of sustained attention and spatial working memory both in a total sample, and in samples split by age and by sex. Paper 3 further examined the association between schizotypy and cognition laboratory tests of attention, executive function and verbal learning/memory. Paper 4 tested the same participants on measures of functional brain asymmetry. Paper 5 used diffusion tensor imaging (DTI) to examine white matter structures in a sample of high schizotypes and controls. Results: Paper 1 confirmed that the SPQ is most appropriately modelled by a four-factor structure in an adolescent and young adult sample. Demographic effects on SPQ subscales scores mirrored those seen in clinical samples. Paper 2 found that where small associations between schizotypy and sustained attention/spatial working memory function occurred, these were in relation to either age of sex. Paper 3 demonstrated an association between increased schizotypal features and a slight reduction in performance on verbal learning/memory, but no association with tasks of executive function or attention. In Paper 4, schizotypy was associated with a left-hemifield bias on a computerised line bisection task. Paper 5 found that a group of high schizotypes had an increase in tract coherence in the uncinate fasciculus compared to controls. Furthermore, increasing subclinical hallucinatory experiences were associated with increased tract coherence in the right hemisphere arcuate fasciculus. Conclusions: Schizotypy was associated with changes in brain function and structure similar to that demonstrated in more serious mental illness, although to a lesser degree. The current studies suggested that schizotypy is associated with relatively intact prefrontal function, but slight performance bias on measures of medial temporal lobe function. There was also evidence for structural brain changes in schizotypes, with these being indicative of either a protective factor, or a marker of a pathological process. Correlations between hallucinatory experiences and white matter tracts between language regions support theories implicating hyperconnectivity and presentation of symptoms in clinical groups. The functional and structural data collected from this study suggests that the ‘schizotypal’ brain may represent an ‘early’ stage of pathology, but which is likely to be compensated enough such that transition to serious mental illness is unlikely. Further studies could examine similarities and differences between the schizotypal profile and clinical conditions, which would provide further insights into aetiological mechanisms in schizophrenia/psychosis.

People with schizophrenia are known to have difficulties with episodic memory (EM). The purpose of this investigation was to examine the relationship between theta-power and: i) behavioural measures of EM performance, ii) event- related potential (ERP) indices of recollection and, iii) measures of schizophrenia symptomatology. In doing so, the aim was to gain a better understanding of the basic neural mechanisms that contribute to successful EM performance, and how these may differ for people with schizophrenia. The present investigation adopted an endophenotypic approach and collected measures of schizotypy from student participants to minimise patient factors that can confound interpretations. Fifty- four participants were asked to complete a reality-monitoring exclusion EM paradigm whilst electroencephalogram (EEG) data were collected. Measures of theta-power and ERPs were time-locked to words presented during the retrieval phase. There was a significant positive correlation between theta-power over Fz between 600-1000ms post-stimulus presentation and estimates of recollection in the imagine condition as well as a significant negative correlation between these measures of theta-power for perceive items and ERP indices of recollection for imagine items. There was also a significant positive correlation between measures of frontal theta-power in the imagine condition and negative schizotypy. The epoch employed means it is likely these measures of theta- power reflect processes contributing to the content-specific retrieval of imagined items, and post-retrieval processes acting in service of differentiating imagined items in EM. Results are discussed in terms of suggestions for interventions and directions for future research.

Dimensional models of schizotypy and associated traits have taken on current relevance in the DSM-5 (http://www.dsm5.org) proposal for personality disorder (PD), which includes a personality trait initially conceptualized as a five-facet schizotypy domain and then simplified into a three-facet psychoticism domain that has yet to be evaluated extensively. In this study, I (1) reviewed the literature to develop hypotheses about the content and boundaries of the schizotypy domain, and (2) measured this content in a mixed sample of students and patents with 657 usable protocols at Time 1 (193 Notre Dame students, 301 University of Iowa students; 163 outpatients) and 263 usable protocols (74 Notre Dame students, 76 University of Iowa students, 113 outpatients) at Time 2, at least 1.5 weeks later. I then (3) evaluated confirmatory models including DSM-5 schizotypy and psychoticism facet models and other empirically grounded models and (4) used the best confirmatory model to provide item pools for classically constructing scales of schizotypy facets. This four-factor structure provided content pools used to create four corresponding scales: Unusual Perceptions, Unusual Beliefs, Dissociation Proneness, and Cognitive and Communicative Peculiarity. Additionally, (5) I used item response theory (IRT)-based analyses to evaluate items in these facet scales, both in terms of the level of schizotypy they best measure and the strength of their relations to the schizotypy construct. I also (6) examined the short-term test-retest reliability of the schizotypy scales, as well as that of the established measures used in this study; new and existing measures were comparably stable. Finally, (7) I evaluated schizotypy's convergent and discriminant validity in relation to three other types of traits: (a) those correlated with the domain (e.g., Obsessive Compulsive Disorder [OCD] and non-delusional mistrust), (b) other higher level traits (i.e., measures of the 3 factor and 5-factor models of higher order personality/temperament), and (c) familially related traits (e.g., social anxiety). Overall, the schizotypy facet measures appeared to assess moderate amounts of variance that were unexplained by the established measures of personality, temperament, and psychopathology that were included in this study. The implications of adding a schizotypy trait to the overall personality trait taxonomy are discussed.