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Identifier 000421916
Title Η επίδραση των αρνητικών και θετικών σχιζοτυπικών χαρακτηριστικών επί ενδοφαινοτυπικών δεικτών για ψύχωση σε ομάδες υψηλού κινδύνου
Alternative Title The effects of negative and positive schizotypal traits on psychosis endophenctypes in high resk groups.
Author Ζουραράκη, Χρυσούλα
Thesis advisor Γιακουμάκη, Στέλλα
Reviewer Σιδηροπούλου Κυριακή
Σπανάκη Κλεάνθη
Παναγής Γεώργιος
Τριλίβα Σοφία
Καστελλάκης Ανδρέας
Οικονόμου Ηλίας
Abstract Schizotypy is defined as a latent vulnerability state, characterized by attenuated schizophrenia-like symptoms, underlying the liability for schizophrenia-spectrum disorders. Empirical evidence shows that schizophrenia spectrum patients and their unaffected first degree relatives present with elevated schizotypal traits. Previous studies that examined the effects of schizotypy on schizophrenia spectrum endophenotypes, did not focus on the assessment of different schizotypal dimensions and their results are controversial. The main goal of this thesis is to assess schizotypal traits and their effects on neuropsychological and psychophysiological endophenotypes of schizophrenia spectrum disorders in unaffected first degree relatives of patients. Furthermore, the present thesis aims to examine the role of genetic polymorphisms of schizophrenia-related genes, familiality and advanced paternal age at birth as an environmental risk factor. The first aim of the thesis was the adaptation of the Schizotypal Personality Questionnaire in a Greek population (Study 1). For this reason, we assessed 865 participants from the general population and performed confirmatory factor analysis to examine the factorial structure of the scale. Based on the findings, the model including four factors, the positive/cognitive perceptual, the negative, the disorganized and the paranoid dimensions had an adequate fit to the data. The second goal of the thesis was to assess schizotypal traits in unaffected first degree relatives of schizophrenia spectrum patients and compare their neurocognitive profile with control individuals (Study 2). One hundred and fifteen adult unaffected first-degree relatives of schizophrenia-spectrum patients and 122 controls were tested for schizotypy with the Schizotypal Personality Questionnaire. They also underwent a thorough neurocognitive assessment with a range of tasks covering several aspects of executive functioning. Between-group differences were examined with either multivariate analysis of variance or with multivariate analyses of covariance, including the schizotypal dimensions as covariates. It was found that the relatives had higher scores on all schizotypal dimensions compared with controls with greater effect sizes for negative and paranoid schizotypy. Regarding the neurocognitive profiles, we found that unaffected relatives had poorer planning, problem solving, strategy formation and working memory, irrespective of schizotypal traits. The difference in executive working memory was sensitive to the effects of paranoid and negative schizotypy, whereas the difference in verbal fluency was sensitive only to the effects of paranoid schizotypy. The next goal of the thesis was two-fold. On the one hand we examined the effects of the four schizotypal dimensions on executive working memory, as mediated by set-shifting, planning and control inhibition. On the other hand, we assessed whether these associations are moderated by family-history of psychosis (Study 3). Moderated-mediation analyses were conducted. The results showed that all mediators were significant in the relationship between negative schizotypy and executive working memory. The effects of paranoid schizotypy were mediated only by set-shifting and planning. Planning and control inhibition were the only significant mediators on the effects of positive and disorganized schizotypy on executive working memory, respectively. The moderated-mediation analyses revealed that these findings apply only in the community group. The fourth goal of the thesis was to examine differences in neurocognition and schizotypal traits in unaffected multiplex and simplex relatives of schizophrenia-spectrum patients and control individuals. The research hypotheses were based on the empirical findings suggesting that familial schizophrenia is associated with genetic risk factors whereas sporadic schizophrenia with environmental ones. Simplex (n=65), multiplex (n=35) relatives and controls (n=114) were compared on a range of cognitive functions and schizotypal traits, assessed with the Schizotypal Personality Questionnaire. Between-group differences were examined with either analyses of covariance or multivariate analyses of covariance, with paternal age at birth, negative and paranoid schizotypal traits as covariates. It was found that simplex and multiplex relatives had higher negative and paranoid traits compared with controls, but paternal age abolished the differences between the simplex and control groups. Moreover, controls outperformed multiplex relatives in strategy formation and set shifting and simplex relatives in psychomotor speed, set-shifting and executive working memory. After including paternal age in the analyses, controls outperformed only multiplex relatives in strategy formation, working memory and executive working memory and both groups of relatives in psychomotor speed and set-shifting. The fifth goal of this thesis was to examine the effects of three different genetic polymorphisms implicated in the schizophrenia spectrum, the rs4680 COMT, the rs2396753 FOXP2 and the rs2007044 CACNA1C on cognitive functions and schizotypal traits. Between-group differences were examined with series of analyses of covariance with two grouping variables: family history group (relatives vs controls) and genotype. We did not find statistically significant differences between the Val/Val, Met/Met and Val/Met groups of rs4680 COMT. Moreover, we did not find any significant interactions between genotype and family history. Similarly, we did not find any statistical significant results for the rs2396753 FOXP2. There was a significant main effect of genotype rs2007044 CACNA1C on spatial working memory, with the G-allele carriers making more between errors. We found also a trend for a statistical significant interaction between Family history x Genotype for Letter number sequencing task, with the unaffected relatives carrying the G allele performing worse. The last goal of this thesis was to examine differences in prepulse inhibition of the startle reflex between unaffected first degree relatives of patients with schizophrenia spectrum disorders and participants from the general population controlling for schizotypal traits. We performed repeated measures analyses of covariance to assess the effect of group (relatives vs controls) on prepulse inhibition. The results showed that the control group had higher prepulse inhibition compared with the relatives and that schizotypal traits did not have any effect on these findings. In summary, the findings of this thesis support the increased expression of schizotypal traits in high risk groups and emphasize their effects on neurocognitive and psychophysiological functions, while considering the role of genetic and non-genetic risk factors. This multi-faceted approach contributes to better understanding of the factors implicated in schizophrenia spectrum disorders. The findings have potential implications in the development of customized early-intervention programmes in populations at increased risk for schizophrenia-spectrum disorders.
Language Greek
Subject Cognitive functions
Genetic polymorphisms
Prepulse inhibition
Schizophrenia spectrum
Schizotypal traits
Unaffected first degree relatives
Γενετικοί πολυμορφισμοί
Γνωστικές λειτουργίες
Προπαλμική αναστολή
Πρώτου βαθμού συγγενείς
Σχιζοτυπικά γνωρίσματα προσωπικότητας
Φάσμα σχιζοφρένειας
Issue date 2019
Collection   School/Department--School of Social Sciences--Department of Psychology--Doctoral theses
  Type of Work--Doctoral theses
Permanent Link https://elocus.lib.uoc.gr//dlib/d/7/3/metadata-dlib-1554192005-154569-16277.tkl Bookmark and Share
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