The Course of Cognitive Impairment across the Psychosis Spectrum

Student thesis: Doctoral ThesisDoctor of Philosophy


The majority of schizophrenia patients exhibit significant, diffuse cognitive impairment. Understanding the course and nature of this impairment is essential to elucidating etiology and treatment. Previous studies have been unable to trace the course of cognition from infancy to adulthood and assess true developmental change. Cognitive deficits in individuals with subclinical psychotic experiences may provide important clues about clinical psychotic disorders. Yet, developmental change and the effects of age, sociodemographic and familial factors have not been examined. Moreover, while there is evidence for connection abnormalities in the brains of schizophrenia patients, little is known about the structure of cognitive functioning across the psychosis spectrum i.e. in subclinical psychotic experiences and clinical psychotic disorders.

The first study examined the association between subclinical psychotic experiences and cognitive functioning in a general population sample. Adults with psychotic experiences showed significant verbal and memory, but not processing speed deficits. Only older adults with psychotic experiences showed medium to large verbal and memory deficits when adjusting for sociodemographic factors, psychiatric morbidity and cannabis use. First-degree relatives showed a significant verbal, but not memory impairment.

The second and third studies used data from a longitudinal cohort to examine 1) the course of cognitive functioning from infancy to adulthood and 2) cognitive network structure in childhood and adulthood. Individuals with depression, psychotic experiences, affective psychotic disorder and non-affective psychotic disorder were compared to controls. Affective psychotic disorder, psychotic experiences and depression groups showed a degree of cognitive impairment across infancy and adulthood, but only those with non-affective psychosis showed large, progressive deficits across multiple domains. Individuals with non-affective, affective and subclinical psychosis also showed qualitative and quantitative abnormalities in cognitive network structure, with the two clinical groups showing larger, widespread anomalies. Controls showed increasing reliance on working memory between childhood and adulthood, while all other groups remained reliant on low-level cognitive processes.

Altogether, these findings suggest that the course of cognitive impairment differs across the psychosis spectrum. Despite distinct profiles of impairment, abnormalities in cognitive network structure were seen across the spectrum, highlighting the importance of looking beyond cognitive deficits to how performance is achieved.
Date of Award2017
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorAvi Reichenberg (Supervisor) & Anthony David (Supervisor)

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