Smits ML, Feenstra DJ, Eeren HV, et al. - Given that for borderline personality disorder (BPD), two types of mentalisation-based treatment (MBT) — day hospital MBT (MBT-DH) and intensive out-patient MBT (MBT-IOP) — have been developed and empirically evaluated, researchers here examined the efficacy of MBT-DH vs MBT-IOP 18 months following commencement of treatment. Further, they tested their hypothesis that MBT-DH would be superior to MBT-IOP given its higher treatment intensity. In this multicentre randomized controlled trial performed in the Netherlands, patients with BPD were assigned to either MBT-DH (n = 70) or MBT-IOP (n = 44). Findings do not support MBT-DH as superior to MBT-IOP in terms of primary outcome measure [symptom severity (Brief Symptom Inventory)], however, MBT-DH exhibited a tendency to be more effective on secondary outcomes (borderline symptomatology, personality functioning, interpersonal functioning, quality of life and self-harm), especially in terms of relational functioning. Patients receiving MBT-DH and MBT-IOP, thus, appear to follow distinct trajectories of change, which may have significant implications for clinical decision-making. The optimal intensity of specialized treatments such as MBT for patients with BPD would be ultimately established with longer-term follow-up and cost-effectiveness considerations.