SUMMARY
Objective: Group Experience Therapy (GET; Visintini et al., 2019) is a structured treatment for patients with Borderline Personality Disorder (BPD) features. The study aimed at evaluating GET effectiveness in a longitudinal, single-blind, two-arm parallel design, comparing GET with Dialectical Behavior Therapy (DBT; Linehan, 1993, 2014). The individual variability was expected to be consistent.Methods: The sample was comprised of 95 outpatients, assigned to groups with the minimisation procedure and assessed every three months. Treatments were delivered by 28 therapists at the San Raffaele Scientific Institute, Milan, Italy. Hierarchical Linear Models with random effects were used; supplementary analyses were repeated for the completers’ subsample (N = 53).Results: Suicidality, self-harm, emotional and behavioral dysregulation decreased in both groups after one year. Strategies to regulate intense emotions and mindfulness skills improved better in GET for the completers. Unconditional growth models indicated that subjects differed in the elevation and in the rate of change.Discussion: GET and DBT reached comparable outcomes on target variables over one year. Group setting or the intensity of treatment could be hypothesized as GET-specific therapeutic mechanisms.