An evaluation of factor structure, measurement invariance, and psychometric properties of the Psychache Scale

The Psychache Scale (PAS) was developed to assess the core construct of Shneidman's model, but the empirical literature shows discrepancy regarding its factor structure. This investigation evaluated whether a unidimensional, two-factor, or bifactor structure best fit the data. Once established, measurement invariance across sexuality, race, and ethnicity, as well as longitudinal invariance, was evaluated. A sample of 1,882 college students completed self-report assessments at baseline and 1-week follow-up. Factor analysis and multigroup factor analysis were conducted. Psychometric properties, including test-retest reliability, concurrent validity, internal consistency, and predictive validity, were evaluated. Results favored a modified bifactor model. Multigroup CFA analyses yielded measurement invariance across groups. Additionally, the PAS was found to have excellent internal consistency and good concurrent validity. Finally, the PAS was predictive of future suicidal ideation even when accounting for related constructs. These results indicate that the PAS is a valid, reliable, and measurement-invariant tool for assessing psychache using a bifactor structure.