Comparing Psychometric Properties of Three Personality Functioning Scales in a Community Sample

When multiple instruments are available for measuring the same construct, researchers and practitioners may face uncertainty about which one to use. This study evaluates factor structure, internal consistency coefficients, and intercorrelations between the Self and Interpersonal Functioning Scales (SIFS), the DSM-5 Levels of Personality Functioning Questionnaire-Short Form (DLOPFQ-SF) and the Personality Functioning Scales (PFS) and evaluate their concurrent validity in relation to levels of wellbeing, happiness, self-esteem, attachment styles, and the quality of interpersonal relationships. In a non-clinical sample of N = 506 participants, the factor structures of all three instruments were confirmed, and good convergent, discriminant, and concurrent validity were established. Among them, the SIFS demonstrated the strongest concurrent validity for mental health outcomes, despite showing somewhat lower internal consistency coefficients compared to the DLOPFQ-SF and PFS. However, differences in concurrent validity were not substantial. Although the Self and Interpersonal domains were found to be highly correlated, regression analyses confirmed the theoretically expected unique contributions of individual scales within both domains. The findings support the conclusion that all three instruments measure very similar underlying constructs, and that the generalizability of results in the field of personality functioning is not seriously compromised when using any of these questionnaires.