Does the severity of specific borderline personality disorder symptoms vary by sexual orientation? A differential item functioning analysis of self- and clinician-ratings.

Although borderline personality disorder (BPD) is more frequently diagnosed among sexual minority individuals than heterosexual individuals, it is unclear the degree to which this disparity reflects differences in symptom expression, diagnostic bias, or some combination of the two. Among treatment-seeking adults with BPD (N = 121, Mage = 28.4; 76% female, 89% White, and 57% sexual minority), we examined differential item functioning (DIF) and group differences in symptom severity using self-reported and clinician-administered BPD measures (Zanarini Scale for Borderline Personality Disorder-Self-Rated, Zanarini Scale for Borderline Personality Disorder-Clinician-Rated, Structural Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders-Fifth edition-Personality Disorders). Although there was no evidence of DIF for any self-reported item, sexual minority participants endorsed self-injurious behaviors (B = 0.63, p = .01), stress-related paranoia or dissociation (B = 0.62, p = .01), efforts to avoid abandonment (B = 0.53, p = .02), and unstable relationships (B = 0.54, p = .03) more often than heterosexual participants on average, contributing to greater past-week total symptomatology (B = 3.88, p < .01). Clinician-administered items assessing self-injurious behaviors exhibited uniform DIF and were "easier" to endorse for sexual minority participants. Furthermore, assessors rated self-injurious behaviors for sexual minority participants more often over the past week (B = 0.51, p < .01) and past 2 years (odds ratio = 3.58, p < .01) than heterosexual participants, and affective instability over the past 2 years (odds ratio = 4.00, p < .05). These results suggest that patients and assessors interpreted most BPD items similarly, while emphasizing the need for nuanced examination of symptomatology and cultural competence in clinical practice to ensure accurate evaluation of BPD across diverse groups. (PsycInfo Database Record (c) 2026 APA, all rights reserved).