Personality Disorders: Theory, Research, and Treatment, Vol 17(4), Jul 2026, 253-265; doi:10.1037/per0000764
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 B = 0.51, p p p