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Title: Symptom dimensions in individuals at Ultra High Risk for psychosis : neurobiological and clinical correlates
Author: Azis, Matilda
ISNI:       0000 0005 0287 5086
Awarding Body: King's College London
Current Institution: King's College London (University of London)
Date of Award: 2017
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The Ultra High Risk (UHR) state is a clinical syndrome that is associated with a high risk for imminent psychotic disorder. Examination of the symptoms in the UHR population using a dimensional approach could improve our understanding of the clinical and neurobiological heterogeneity within UHR samples, as it has done in schizophrenia. Two previous studies in UHR subjects have found that the symptoms measured by the CAARMS cluster on to underlying psychopathological dimensions. Moreover, both found a link between severity of scores on negative and disorganised factors and the risk of later transition to psychosis. However, one study described five symptom dimensions whereas the other described a three dimensional model, and neither structure has been independently replicated. In the present study, CAARMS data from a total of 461 UHR subjects were used to perform principle axis factoring (PAF) and confirmatory factor analysis (CFA). Scores for each factor of the structure found to best fit the data were then correlated with resting regional cerebral blood flow (rCBF) at presentation and with clinical outcomes after two years of follow up. PAF revealed a five factor structure, which was confirmed using CFA. In the subsample of subjects who were studied with neuroimaging, scores on the disorganisation factor were associated with reduced rCBF in the thalamus, scores on the anxiety factor were associated with reduced rCBF in the insula, and Total CAARMS scores were associated with reduced rCBF in the left hippocampus. Higher scores on the anxiety factor and a higher total CAARMS score were associated with an increased risk of later transition to psychosis, while higher scores on the disorganisation factor was associated with worse functional outcome. These findings suggest that symptom dimensions in the UHR state have distinct neural substrates and clinical correlates. Variation in these dimensions may contribute to the marked heterogeneity of clinical presentations and outcomes within samples of UHR subjects.
Supervisor: McGuire, Philip ; Allen, Paul ; Modinos, Gemma Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available