Cognitive characteristics of patients with borderline personality disorder: development and validation of a self-report inventory.
Based on cognitive concepts of personality disorders as well as on the bio-social model of borderline personality disorder (BPD), a 34-item instrument, the questionnaire of thoughts and feelings (QTF) was developed for the assessment of feelings, strategic cognitions, and assumptions characteristic for BPD. In different studies, item- and factor analyses were conducted with a dataset of N=646 clinical and non-clinical participants. Cross-sectional data as well as longitudinal data are available including several other measures on personality and personality disorders: DSM-IV SCID II dimensional score, a personality inventory (PSSI), the German version of the personality disorder beliefs questionnaire (PBQ), as well as overall severity of symptoms (GSI) of the SCL-90-R. Internal consistency of the scale is excellent, Cronbach's alpha=0.91. One-week test-retest reliability was also high r(tt)=0.81. Good convergent and discriminant validity was obtained for correlation with SCID dimensional scores and discrimination of BDP patients and other clinical and non-clinical groups. A comparison of scores in a sample of 26 patients with BPD during crisis intervention and 8 months later indicated the sensitivity of the QTF to measure change over time. Overall, the questionnaire appears to be a methodologically sound measure, valuable for research purposes as well as in clinical practice.