Psychosis-like experiences in the general population: An exploratory factor analysis

doi:10.1016/j.paid.2009.01.035

Personality and Individual Differences

Volume 46, Issue 7, May 2009, Pages 729-734

https://doi.org/10.1016/j.paid.2009.01.035 Get rights and content

Abstract

In nonclinical populations psychosis-like experiences have been extensively studied under the psychometric rubric of schizotypy (psychosis-proneness). This study aims to assess the extent of schizotypal traits and associated personality correlates displayed within a quota sample stratified by gender and age, the emphasis being upon anomalous experiences (positive schizotypy). Respondents (N = 130) completed a battery of established self-report measures assessing nine areas of personal experience. Principal components analysis identified two factors accounting for 65.41% of the total variance; the factor accounting for the greatest proportion of variance (50.23%) represented a psychological disposition towards reporting ‘Anomalous Experiences’. The other factor (15.18% of variance) we named ‘Transpersonal Experiences’. No significant gender differences were revealed for the five self-report measures that provided unique contributions toward anomalous experiences. However trends towards significant gender differences were noted for the two self-report measures that provided unique contributions toward transpersonal experiences. Additionally four of the seven self-report measures that provided unique factorial contributions generated significant differences between agebands. Implications for the role of anomalous and transpersonal experiences with regard to psychosis-proneness are discussed.

Introduction

Unusual beliefs and experiences (e.g., delusional convictions, paranormal beliefs, hallucinatory-experiences, pronounced religio-spiritual zealotry) are not solely the domain of those with a clinical diagnosis of a psychotic illness but appear to manifest themselves on a continuum throughout the entire population (Shevlin, Murphy, Dorahy, & Adamson, 2007). From this perspective schizophrenia and related disorders represent but one end of the psychosis spectrum (van Os, Hanssen, Bijl, & Vollenbergh, 2001). A significant proportion of individuals from the general population report experiencing psychosis-like experiences (or psychometrically defined schizotypal phenomena) without attaining the clinical threshold for psychosis (Verdoux & van Os, 2002), leaving them generally free from the experimental confounds inherent to clinical subjects, e.g., psychotropic medication, institutionalisation, chronicity, etc. Nonetheless high schizotypy has been likened to an attenuated version of schizophrenia, involving similar but milder cognitive and behavioural deficits (Compton, Chien, & Bollini, 2007).

Brief or attenuated psychotic symptoms are reported by individuals in the prodromal phase of schizophrenia and other psychotic disorders, and give rise to considerable personal and/or social distress (e.g., Henry, Bailey, & Rendell, 2008). However a relatively small proportion of such individuals actually go on to develop a psychotic disorder in the ensuing time period, and it is presently difficult to predict those that will ‘convert’ to full psychosis from those that will remain well (Yung et al., 2007). The importance of detecting emerging psychotic disorder has led to renewed interest in the construct if schizotypy (e.g., van Kampen, 2006), and there is now an extensive literature attesting to the value of self-report measures (SRMs) of psychosis-proneness (Raine & Lencz, 2007). Unfortunately much of this research has relied on data collected from undergraduate students (Rawlings, Williams, Haslam, & Claridge, 2008). Although an easily accessible sample group, undergraduate students cannot be regarded as representative of the adult population as a whole (Balogh & Merritt, 1990) given their enhanced educational status, limited age range, and possible increased propensity for, or at least access to, recreational drug use.

The aims of this study are twofold. We wish to add to the existing literature base by evaluating the prevalence of psychometrically identified anomalous experiences, but additionally to investigate the distribution of such experiences within a quota sample of the general (nonclinical) population stratified by gender and age (cf. Badcock and Dragović, 2006, Reynolds et al., 2000). Utilising ‘positive schizotypy’ and ‘anomalous experiences’ as primary search terms articles were electronically sourced from the years 1980–2008 via PubMed and PsycINFO; the literature review revealed nine domains of personal experience with appropriate and psychometrically verified SRMs: (1) hallucinatory-experiences; (2) delusional ideation; (3) religiosity; (4) transliminality; (5) schizotypy; (6) sense of coherence (subjective well-being); (7) paranormal beliefs; (8) traditional religious beliefs; and (9) dissociative experiences. Based on investigations into the phenomenology of anomalous self-experiences (Kennedy and Kanthamani, 1995, Parnas and Handest, 2003) the overarching research question we proposed was – To what extent will the nine SRMs correlate in a stratified quota sample? Secondly, we predicted that when subjecting all nine SRMs to principal components analysis the resultant data would provide a limited number of factor solutions, and that certain SRMs would provide unique contributions toward factors. Finally, we want to provide contributory evidence concerning the distribution of any uniquely contributing SRMs with regard to gender and age.

Section snippets

Respondents

One hundred thirty respondents were identified from the general (non-undergraduate) population and enrolled into the study utilising a stratified quota sampling technique (details from the author). All respondents reported no history of or treatment for psychopathology, were white-Caucasian (due to non-response), at least 18-years of age, and spoke English as their first language. Following Badcock and Dragović (2006), we treated age as a non-continuous (banded) variable (see Table 1).

Materials

Correlational analysis

In order to gain an overview of relationships between variables a complete correlational analysis was conducted. In support of the study’s first aim, results revealed that, aside from the measure of RGY, all SRMs displayed significant intercorrelations (see Table 2).

Principal components analysis (PCA)

PCA (Oblimin with Kaiser-normalisation procedure) was carried out. Oblimin rotation was utilised because it assumes that the underlying factors are not necessarily independent from one another, which may often be the case in

Discussion

Anomalous experiences may be an integral, and even adaptive, part of the human condition (Schofield & Claridge, 2007); with a study utilising the Cardiff Anomalous Perceptions Scale (CAPS; Bell, Halligan, & Ellis, 2006a) indicating that the acceptance of such experiences provided a degree of stress protection (Bell, Halligan, & Ellis, 2007). The present exploratory study aimed to assess the prevalence of anomalous (psychosis-like) experiences within a stratified quota sample of the general

Ethical statement

The study was approved by the Ethics Committee of the Department of Psychology, Manchester Metropolitan University. The study was introduced as an inquiry into the patterns and prevalence of unusual thought and ideation within the general population. All respondents provided informed written consent.

Acknowledgements

Grateful thanks are extended to Keith Bradbury, Marguerite Halpin, and Tony Walker for their help with data collection.

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Psychosis-like experiences in the general population: An exploratory factor analysis

Abstract

Introduction

Section snippets

Respondents

Materials

Correlational analysis

Principal components analysis (PCA)

Discussion

Ethical statement

Acknowledgements

Social Science and Medicine

Personality and Individual Differences

Trends in Cognitive Sciences

European Psychiatry

Schizophrenia Research

Psychiatry Research

Clinical Psychology Review

Consciousness and Cognition

Schizophrenia Research

Personality and Individual Differences

Psychiatry Research

Personality and Individual Differences

Comprehensive Psychiatry

Personality and Individual Differences

Personality and Individual Differences

Schizophrenias Research

Personality and Individual Differences

Personality and Individual Differences

Schizophrenia Research

Schizophrenia Research

Schizophrenia Research

Personality and Individual Differences

Dissociation and vulnerability to psychotic experiences: The Dissociative Experiences Scale and the MMPI-2

Journal of Nervous and Mental Disease

Diagnostic and statistical manual of mental disorders (4th ed text revision) (DSM–IV-TR)

Unravelling the mystery of health

Accounting for schizophrenics’ Magical Ideation scores: Are college-student norms relevant?

Assessment

The Cardiff Anomalous Perceptions Scale (CAPS): A new validated measure of anomalous perceptual experience

Schizophrenia Bulletin

Reality testing and auditory hallucinations: A signal detection analysis

British Journal of Clinical Psychology