The Levels of Personality Functioning Questionnaire 12-18 (LoPF-Q 12-18) is the only self-report measure informed by the Level of Personality Functioning (Diagnostic and Statistical Manual of Mental Disorders [5th ed.; DSM-5; American Psychiatric Association, 2013]) Alternative Model of Personality Disorders developed for adolescents. The present investigation includes two studies evaluating the English LoPF-Q 12-18. In Study 1, single-factor and bifactor structures (unidimensional severity criterion and four specific factors: identity, self-direction, empathy, intimacy) were evaluated in an ethnically diverse community sample (N = 453; age 10-18; 57% female). Study 2 used a community control (n = 298; age 10-18; 54.4% female) and clinical sample (n = 94; age 11-18; 58.5% female) to examine reliability, validity, and clinical utility. Study 1 results supported the bifactor model, with a robust general factor and little multidimensionality caused by the group factors, suggesting an essentially unidimensional structure. Study 2 revealed good internal consistency and construct validity and provided clinical cut-offs, supporting the use of the LoPF-Q 12-18 total score in research and clinical applications.
Keywords: adolescents; alternative model of personality disorder; personality functioning.