A Systematic Review of Self-Report Measures of Paranoia

Paranoia can be conceptualized as consisting of a hierarchy of cognitions, ranging from commonly experienced thoughts about less severe perceived threats, up to less common, persecutory thoughts about extreme threats, which are associated with distressing psychosis. This review systematically appraises self-report paranoia questionnaires validated for use among the general population; the type of paranoia assessed, measurement or psychometric properties, and subsequent validation with clinical samples are all considered. A systematic literature search was performed using PubMed, Web of Science, and PsycINFO databases. Study methodologies and measurement properties were evaluated according to COnsenus-based Standards for the selection of health-based Measurement Instruments (Mokkink et al., 2012). Twenty-six studies, describing the validation of nine paranoia-related questionnaires, were identified. Questionnaires were reviewed in relation to the hierarchy of paranoia; with 2 questionnaires assessing "low-level" paranoia, 4 assessing persecutory thoughts, and the remainder assessing paranoia across this continua. Questionnaires assessing the full hierarchy of paranoid thoughts, alongside associated dimensions such as preoccupation, conviction, and distress, offer the most comprehensive assessment of paranoia in both nonclinical and clinical populations. Of the measures which do this, the Green et al. (2008) Paranoid Thoughts Scale had the strongest evidence for its measurement properties and is, therefore, recommended as the most reliable and valid self-report assessment of paranoia currently available. However, this review illustrated that generally paranoia questionnaires lack high quality evidence for their measurement properties. Implications of these findings for clinical practice and research are discussed. Public Significance Statement This systematic review identified 9 self-report questionnaires that have been developed to assess paranoia and were designed for use with the general population. An analysis of studies that used these questionnaires suggested that the Green et al. (2008) Paranoid Thoughts Scale has the best evidence for the reliability and validity of its test scores.