Real-World Outcomes of Mentalization-Based Therapy and Dialectical Behavior Therapy for Cluster B Personality Disorders: A Naturalistic Study of Hospital Service Use and Treatment Dropout

Phillip Yin¹Simon Poirier²Arnaud Allary²Frédéric Pérusse²Pierre David²François-Samuel Lahaie²Lionel Cailhol^2*

• ¹université de montréal, Montreal, Canada
• ²University Institute in Mental Health of Montreal, Montreal, Canada

Mentalization-based therapy (MBT) and dialectical behavior therapy (DBT) are effective treatments for cluster B personality disorders (PDs), but few studies have assessed their real-world clinical outcomes in routine practice outside a controlled trial setting. Our descriptive naturalistic retrospective study evaluated 288 patients with cluster B PDs who predominantly had borderline PD referred to MBT or DBT. Observed changes in emergency department (ED) use and hospitalizations one year before and during the first year of therapy were described for patients with at least one relevant event, along with dropout rates. ED visit analyses concerned 104 patients, and hospitalization analyses concerned 30 patients. Across both treatment modalities, ED visits decreased from 119 in the year prior to treatment to 37 during the first year of treatment (p < .001 for both). Hospitalizations were observed to decrease for patients in MBT (p < .05), while no clear change was seen in the DBT group (p = .595). Drop-out rates during treatment were around 30% in both modalities. These patterns descriptively suggest that both therapies are associated with reduced service use during treatment in clinical practice. Future research should investigate which patient- and system-level characteristics can guide patients and clinicians toward the most suitable treatment for each individual, and whether these observed patterns persist beyond the treatment period.