ABSTRACT
Borderline personality disorder (BPD) is characterized by emotion dysregulation, identity disturbance, suicidal behavior, and fear of abandonment. BPD is a Cluster B personality disorder, alongside narcissistic personality disorder (NPD), which can be conceptualized across two subtypes: grandiose narcissism and vulnerable narcissism (VN). Unlike grandiose narcissism, VN has been largely neglected in research—despite overlapping features with personality and mood disorders, especially BPD. This research aims to address this gap by examining BPD and VN in a clinical sample to assess whether their co-occurrence exacerbates symptom severity in the domains of emotion dysregulation, rejection sensitivity, and identity disturbance. The study included 97 adults hospitalized in a psychiatric inpatient unit in New York. Statistical analyses included latent profile analysis, ANOVAs, and pairwise comparisons. Four distinct profiles emerged: BPD–VN, BPD, Subclinical, and Normative. The BPD–VN group reported significantly greater levels of emotion dysregulation, identity disturbance, and rejection sensitivity compared to the other groups. They also endorsed more lifetime suicide attempts and trauma exposure. The BPD group was the most frequently readmitted and had the longest hospital stays. Findings highlight the importance of identifying this population early in treatment settings to inform targeted interventions and implement safeguards both during and after hospitalization.