Psychosis proneness in the Chinese population : psychometric measurement and psychological risk mechanism

Abstract

Traditionally, psychotic symptoms such as hallucinations and delusions were linked invariably to psychopathology. However, there is increasing evidence that psychosis may be a continuous phenotype with subclinical manifestations. This paradigm shift has fueled research interest in “psychosis proneness”, the extent to which an individual experiences psychotic-like experiences (PLEs) that are insufficient to warrant a diagnosis. Since psychosis proneness is conceptualized as a subclinical manifestation of clinical psychosis with shared etiology, studying cognitive correlates of psychosis proneness may shed light on psychological risk mechanisms of psychosis while circumventing confounding variables of illness experience in clinical samples. This thesis focuses on the mechanism of aberrant “affective salience attribution”, the tendency to assign emotional (positive or negative) meaning to neutral sensory information. To study the relationship between affective salience attribution and psychosis proneness, a psychosis proneness scale was first validated, and then correlated with an experimental task tapping affective salience attribution. Study 1 pertained to the psychometric robustness of a widely-used 42-item psychosis proneness self-report tool, “Community Assessment of Psychic Experiences” (CAPE). To study CAPE’s score reliability, 18 studies that reported original internal reliability coefficients (Cronbach’s alpha) were aggregated in a reliability generalization meta-analysis. Results suggested that CAPE scores were typically reliable (α > .70). Furthermore, to confirm the nature of factors tapped by CAPE, 17 factor-analytic studies were reviewed and subjected to a meta-analysis of factor analyses. Results supported CAPE’s three-factor model with subscales tapping positive, negative and depressive symptoms. Study 2 concerned the validation of a Chinese translation of CAPE (CAPE-C). Factor analyses of CAPE-C scores from 660 youths suggested that a 15-item structure (CAPE-C15) captured the psychosis proneness phenotype in young Chinese better than the original structure (Study 2a). Convergent-divergent validity of CAPE-C15 subscale scores was demonstrated by significant associations with relevant measures and non-significant associations with irrelevant ones (Study 2b). Validating CAPE-C15 rendered it possible to study cognitive correlates of psychosis proneness in Chinese youth, supplementing the predominantly Western literature. One putative cognitive risk mechanism of psychosis is aberrant affective salience attribution. Previous research has suggested that the tendency to extract affective speech from white noise (“affective speech illusion”) is significantly higher in psychotic patients and their siblings than in controls. However, no studies have examined the relationship between affective speech illusion and psychosis proneness in a general population. Study 3 addressed this void. Results showed that “negative speech illusion” was associated with higher CAPE-C15 positive symptom scores, but positive and neutral speech illusions were not. This suggests that attributing negative salience to internal representations might contribute to positive symptoms. Through the use of a non-clinical population, the findings suggested that negative salience misattribution is not merely a result of clinical psychosis, supporting it as potential risk mechanism. This thesis contributes towards a more global picture of the extended psychosis phenotype through validating a psychosis proneness assessment tool for Chinese youth and studying cognitive correlates of psychosis proneness in this population. It also broadens the literature by shedding light on a relatively under-researched psychological risk mechanism of psychotic symptoms.