Objective: This study evaluated the real-world effectiveness of mentalization-based treatment by assessing the clinical status of patients before and after completing the treatment program, which was nested within a general adult community mental health service, and by comparing these patients with a treatment-as-usual group. Methods: In this retrospective longitudinal naturalistic study, patients with a primary diagnosis of borderline personality disorder received either mentalization-based treatment (N=34) or treatment as usual (N=51). Data were collected from clinical charts and hospital databases. Presentations to the emergency department (ED), psychiatric and medical hospitalizations, and rates of loss to follow-up were analyzed for both groups. Results: In the 2 years after a course of mentalizationbased treatment, significant reductions were noted in psychiatric hospitalizations (p=0.018). Compared with the treatment-as-usual group, the intervention group had significant reductions in ED presentations (p=0.004) and medical admissions (p=0.040), when the analysis controlled for age and gender. At study endpoint, the proportion of patients lost to follow-up in the treatment-as-usual group was larger (chi(2)=7.59, df=1, p=0.006), with three deaths in the treatment-as-usual group and none in the mentalization-based treatment group. Conclusions: Mentalization-based treatment embedded within a community mental health team may have a positive effect, with significant improvements in unscheduled service use and notable reductions in ED presentations, hospitalizations, loss to follow-up, and mortality. There may be value in building on this study with more prospective, systematic research and patient-reported outcomes to assess the practical significance of this intervention in general psychiatric settings.
