Personality organization and mentalization of depressive inpatients in a long-term-studyObjectives: In a naturalistic long-term follow-up design this study investigated the improvement of depressive symptom severity, mentalization deficiency and personality organization. Methods: 300 patients with depressive symptoms were assessed at three evaluation times (before therapy, after therapy and one to three years after discharge) with the Patient Health Questionnaire Depression Scale (PHQ-9), the Mentalization Questionnaire (MZQ) and the Inventory of Personality Organization (IPO-16). Results: Patients improved significantly in depressive symptom severity with strong impact. Especially patients with severe depression symptoms improved in mentalization deficits and personality organization during and after inpatient treatment. Chronic depressive patients improved in mentalization rather than in personality organization. Depressive symptom severity correlates with mentalization deficits and structural impairment. Discussion: Mentalization deficits differed depending on the severity of depression, as other studies already showed. The more severe depressive symptoms, the more likely mentalization deficits and structural impairment improved. However, the lack of control groups limits the causal proof of efficacy. Mentalization deficits and personality organization should be recorded timely in order to choose adequate technique.