Background Life with Post-Traumatic Stress Disorder (PTSD) or Complex PTSD (CPTSD) often entails intense and challenging symptoms. Conventional treatments are lengthy with high dropouts, which leads to reduce effectiveness and increased costs. This PhD project evaluates an alternative, intensive, short-term treatment and investigates how a person-centred approach informs its planning and delivery. Project aims To develop and evaluate an intensive eight-day treatment for PTSD and CPTSD with the following objectives: • Enable person-centredness through shared decision-making regarding preferred treatment • Offer an efficient and effective treatment • Reduce dropouts Methods / Development Process In 2021, the intensive treatment was introduced at a psychiatric outpatient clinic in Borås, Sweden. The treatment consists of eight full-day sessions and integrates several therapeutic modalities. Treatment begins with setting trauma-focused goals, where patients specify which trauma events to target. A novel feature is therapist rotation, where patients meet different therapists each session. The treatment is evaluated from multiple methodological perspectives. First results Feasibility study (n=12): results, no increased suicide-risk. Evaluation of 101 patients: lower dropout rates in the intensive format; patients receiving intensive treatment achieved symptom reduction nearly a year earlier than those in conventional treatment. Active patient participation identified as a key factor in the intensive group. Conclusions A person-centred approach appears to enhance patient involvement in the decision-making of preferred treatment. Ongoing studies explore factors influencing patients’ decisions to engage in intensive treatment, with a parallel study planned for those preferring conventional treatment. A person-centred approach will continue to guide both the choice of treatment format (intensive vs. standard) and trauma-focus within therapy. Next Steps Associations between perceived participation and treatment outcomes will be analysed. The innovative element of therapist-rotation will be further examined. The intensive treatment will be implemented as part of standard treatment at Södra Älvsborgs Hospital, Borås, Sweden.