First psychometric evaluation of the English version of the Semi-Structured Interview for Personality Functioning (STiP-5.1)

The Alternative Model for Personality Disorders provides a dimensional framework for the conceptualization of personality disorders where Criterion A concerns the assessment of one's level of personality functioning (LPF). This study examines the psychometric properties of the English translation of the Semi-Structured Interview for Personality Functioning (STiP-5.1) to validate this translation for the assessment of LPF in English-speaking populations; and examine whether this measure increments self-report measures of LPF and personality pathology in predicting general functioning. The sample consisted of 129 emerging adults between 18 and 25 years of age (M = 20.54, SD = 2.08) from a mixed college and clinical sample. Results support a unidimensional factor structure of the STiP-5.1, good internal consistency, and high inter-rater reliability. Construct validity was supported through associations of the STiP-5.1 with self-report measures of LPF and personality pathology. The STiP-5.1 incremented self-report measures of personality pathology in predicting functional impairment, though additional variance explained was modest. Finally, STiP-5.1 scores differentiated individuals who obtained a score at or above the clinical cutoff from those below on self-report measures of personality pathology and LPF with large effect sizes. Findings support the validity of the English translation of the STiP-5.1 for the assessment of LPF.