Elevated borderline features in bipolar disorder: Clinical characteristics and symptom course in South Korea

Elevated borderline features (EBF) in bipolar disorder (BD) are associated with a more severe illness course, but prospective evidence remains limited, particularly in Asian populations. We examined the clinical correlates and 6-month depressive symptom course of EBF in Korean patients with BD.

Participants were 520 patients with BD-I or BD-II from three South Korea tertiary hospitals. EBF was identified using the self-report Personality Assessment Inventory-Borderline Features Scale (score ≥ 38). Clinical characteristics were compared between EBF and non-EBF groups after adjusting for demographic and clinical covariates, and 6-month depressive symptom trajectories under naturalistic treatment were compared.

Overall, 237 (45.5%) met the EBF criterion. After adjustment, EBF was associated with more depressive episodes, greater childhood trauma, lifetime self-harm, suicidal ideation, suicide attempts, violence, and several comorbidities. Depressive symptoms improved in both groups, but the EBF group maintained greater severity across follow-up (adjusted mean difference = 4.00, 95% confidence interval [CI] = 1.83-6.18). with a nonsignificant EBF by time interactions. EBF was associated with lower odds of response (adjusted odds ratio = 0.40, 95% CI = 0.18-0.91), remission did not differ.

EBF was defined by a self-report screening measure rather than a structured diagnostic interview, and clinical correlates were examined cross-sectionally. Causal relationships cannot be inferred.

Among Korean patients with BD, EBF was associated with greater illness burden and persistently greater depressive symptom severity. These findings extend predominantly Western evidence to an Asian population and support assessing borderline features to guide risk evaluation and longitudinal monitoring.