Abstract
INTRODUCTION: The Levels of Personality Functioning Questionnaire (LoPF-Q) is a self-report tool developed to assess impairments in personality functioning, informed by Criterion A of the DSM-5 Alternative Model for Personality Disorders (AMPD) and the ICD-11 dimensional framework. The LoPF-Q 12-18 represents the adolescent version of the LoPF-Q Adult and has demonstrated robust psychometric properties in Turkish adolescent samples; however, the psychometric performance of the adult version in Turkish populations and its structural comparability across age groups remain underexplored. METHODS: The current study evaluated the reliability, validity, and structural characteristics of the Turkish LoPF-Q Adult in a combined sample of 283 community adults and 65 clinical participants. Internal consistency was assessed via Cronbach's alpha. Convergent and discriminant validity were examined through associations with the Brief Symptom Inventory (BSI). Clinical validity was evaluated by comparing LoPF-Q scores between the community group and a subset of patients diagnosed with personality disorders (n = 34). Additionally, bifactor modeling and receiver operating characteristic (ROC) analyses were conducted to examine factor structure and discriminative ability. RESULTS: The LoPF-Q Adult demonstrated excellent internal consistency (Cronbach's α =96). Strong correlations with general psychopathology on the BSI supported convergent validity, with distinct subscale-level patterns consistent with theoretical expectations. Clinical comparisons revealed significantly higher LoPF-Q total scores in individuals with personality disorders than in the community sample, with a large effect size (d = 1.56). Bifactor indices indicated a dominant general factor capturing the majority of shared variance, aligning with prior adolescent validation studies. ROC analysis yielded an area under the curve of.85, with an optimal cut-off score that provided balanced sensitivity and specificity. DISCUSSION: These findings support the reliability and clinical utility of the Turkish LoPF-Q Adult as a dimensional measure of personality functioning severity. The strong general factor, robust discrimination between clinical and non-clinical groups indicates that the instrument captures structural impairment central to contemporary AMPD and ICD-11 models. Together with prior adolescent findings, the results are consistent with cross-age structural compatibility in the assessment of personality functioning rather than direct evidence of developmental continuity, while remaining preliminary pending longitudinal and invariance studies.