Exploring the Feasibility of a Generic Early Intervention Programme for Emerging Personality Disorder in Adolescents: Guideline-Informed Treatment for Personality Disorders-Adolescent Version (GITPD-A).

The Guideline-Informed Treatment for Personality Disorders-Adolescent version (GITPD-A) is an accessible, general approach to treating personality disorders (PDs) in adolescents. This study assessed the feasibility of the intervention and of a multicentre research design, as a preliminary step towards larger, better-controlled trials. A one-group pretest-posttest design was used across five mental healthcare institutions. Eligible participants were adolescents aged 12-18 meeting threshold criteria for a PD under the DSM-5 alternative model. Participants (91.9% female; mean age 15.9 years) received GITPD-A for 6 months. Intervention feasibility was evaluated via paired-samples t-tests on pre- and posttest scores. Feasibility of the multicentre design was assessed by eligibility and enrolment rates, measure completion and study dropout. Significant improvement was found for pathological personality traits (PID-5), with a medium effect size (Hedges' g = 0.50). Secondary outcomes showed significant reductions in depression, anxiety, emotion dysregulation and symptoms of borderline PD. Participants reported high satisfaction (M = 8.1). Following a broad screening process involving 245 participants, 65 were found to be eligible. Of these, 47 adolescents took part in the study overall, with 38 completing the intervention. The treatment dropout rate was 19.1% (n = 9). Despite the limited sample, preliminary findings support the feasibility of GITPD-A for adolescents with emerging PD, showing high acceptability, satisfaction, retention and acceptance of scientific assessments. Selected measures appear suitable for detecting intervention-related changes. However, a different primary outcome and improved screening strategies may be needed.