Differences in diagnostic rules used to determine borderline personality disorder impact prevalence and associations with clinically relevant variables: Findings from the National Epidemiologic Survey on Alcohol and Related Conditions-III.

Borderline personality disorder (BPD) is a serious and understudied mental health condition associated with profound personal and public health consequences. Methodological differences in characterizing BPD may limit understanding the scope of the disorder's prevalence and effect. For example, using different diagnostic rules for BPD can affect apparent prevalence, comorbidity, and clinical presentation. This study examined how differences in diagnostic rules used to assign BPD diagnosis impacted its prevalence and associations with clinically relevant variables (e.g., demographics, comorbidity, treatment-seeking). Participants were a nationally representative sample of 36,309 noninstitutionalized U.S. adults. All variables were assessed via clinical interview (Alcohol Use Disorder and Associated Disabilities Interview Schedule-5). Six diagnostic rules determined BPD status. We used frequencies to examine prevalence rates of and associations between BPD and other clinical variables, and logistic regressions to examine the associations between each BPD variable and the other outcomes. The prevalence of BPD ranged widely-from 0.5% to 11.4%-per the diagnostic rule used. Associations between BPD diagnosis and various outcomes and clinical variables generally remained stable across all diagnostic rules, though effects became more extreme as diagnostic rules became more restrictive. Additionally, meaningful differences emerged as a function of the number of items used (30 vs. 18 items) even with no other changes to diagnostic rules. The field examining BPD and associated problem behaviors should critically consider how to most effectively characterize BPD to understand these problems more accurately and optimize the generalizability of findings. (PsycInfo Database Record (c) 2024 APA, all rights reserved).