Abstract
BACKGROUND: The borderline personality disorder (BPD) population is notably heterogeneous, and this has potentially important implications for intervention. Identifying distinct subtypes of patients may represent a first step in identifying which treatments work best for which individuals. METHODS: A cluster-analysis on dimensional personality disorder (PD) features, as assessed with the SCID-II, was performed on a sample of carefully screened BPD patients (N = 187) referred for mentalization-based treatment. The optimal cluster solution was determined using multiple indices of fit. The validity of the clusters was explored by investigating their relationship with borderline pathology, symptom severity, interpersonal problems, quality of life, personality functioning, attachment, and trauma history, in addition to demographic and clinical features. RESULTS: A three-cluster solution was retained, which identified three clusters of BPD patients with distinct profiles. The largest cluster (n = 145) consisted of patients characterized by "core BPD" features, without marked elevations on other PD dimensions. A second "Extravert/externalizing" cluster of patients (n = 27) was characterized by high levels of histrionic, narcissistic, and antisocial features. A third, smaller "Schizotypal/paranoid" cluster (n = 15) consisted of patients with marked schizotypal and paranoid features. Patients in these clusters showed theoretically meaningful differences in terms of demographic and clinical features. CONCLUSIONS: Three meaningful subtypes of BPD patients were identified with distinct profiles. Differences were small, even when controlling for severity of PD pathology, suggesting a strong common factor underlying BPD. These results may represent a stepping stone toward research with larger samples aimed at replicating the findings and investigating differential trajectories of change, treatment outcomes, and treatment approaches for these subtypes. TRIAL REGISTRATION: The study was retrospectively registered 16 April 2010 in the Nederlands Trial Register, no. NTR2292.