Measuring Paranoid Beliefs in Adolescents: A Comparison of the Revised-Green et al.'s Paranoid Thoughts Scale (R-GPTS) and the Bird Checklist of Adolescent Paranoia (B-CAP).

Research on paranoid beliefs in adolescents is in its infancy. Valid and reliable assessments are essential to advancing the field, yet there is no current consensus as to which are optimal to use in this population. This study compared the psychometric properties of two measures of paranoia in a general population adolescent sample. A cross-sectional study with quota sampling (gender and age) recruited adolescents (14-17 years) from the UK (n = 262) and USA (n = 200), who completed the Revised Green et al. Paranoid Thoughts Scale (R-GPTS) and the Bird Checklist for Adolescent Paranoia (B-CAP). We assessed factor structures, intercorrelations, overlap of participants identified as at-risk for paranoid thoughts via both scales, convergent validity (scales with one another) and discriminant validity (distress, wellbeing, bullying and discrimination). Both scales performed equally well in terms of factorial validity. Intercorrelations between the subscales and with general distress were high for both measures. However, a substantial percentage of participants were identified as having paranoid beliefs according to the R-GPTS but not the B-CAP. Furthermore, the B-CAP showed a very high correlations (0.69 ≤ r ≤ 0.79) with self-reported bullying experiences, which bordered on multicollinearity. Findings highlight the possibility that B-CAP may risk confounding paranoid beliefs with exposure to bullying more so than R-GPTS, and that B-CAP may miss instances of elevated paranoia that are captured by the R-GPTS. Future research needs to further explore this by validating both scales with an external (e.g., interview-based) criterion for paranoia.