ABSTRACT Objective Research on mentalization‐based treatment (MBT) for adolescents with borderline personality disorder (BPD) has yielded mixed results. This qualitative study aimed to explore the experiences of adolescents who participated in a group‐based MBT (MBT‐G) programme 5 years earlier, to uncover the pitfalls, potentials and long‐term effects of MBT within this population. Methods Eleven participants were included in the study. They were interviewed 5 years after completing a 1‐year MBT‐G programme designed for adolescents with BPD or subthreshold BPD. At the time of the interviews, participants were between 19 and 23 years old. Data were analysed using Interpretative Phenomenological Analysis (IPA). Findings The study revealed weak working alliances, as many participants reported feeling uncertain about the goals of treatment and expressed a desire for more concrete therapeutic ‘tools’ and opportunities to address past trauma in individual sessions. Additionally, most participants described a lack of group cohesion, with group participation often experienced as burdensome and anxiety‐provoking. Some participants perceived therapists as distant and lacking empathy, which negatively affected their engagement. In contrast, positive treatment experiences were associated with a clear understanding of the treatment rationale, strong group cohesion and therapists who actively and supportively facilitated the group. Research Implications The findings suggest that establishing effective MBT groups for adolescents with BPD can be challenging and working specifically on establishing group cohesion and uncovering the rationale for the treatment are pivotal. Further quantitative and qualitative studies are recommended to investigate MBT programmes that integrate both individual and group therapy for this population.
Bryde et al. (2026) studied this question.