[Long-term courses of major depressive disorder : Characteristics, risk factors and the definitional challenge of treatment response].

Background: The definition of long-term courses of depression is heterogeneous. Chronic and treatment-resistant courses, in particular, represent a high-cost factor and greatly reduce the quality of life. Based on the pharmacotherapeutic treatment-resistant depression (TRD), more and more systemic approaches are becoming important.

Objective: This narrative review provides an overview of the long-term course of depressive disorders, including various definitions and influencing factors. In addition, an overview of biomarker research on treatment response with a focus on neuroimaging is presented.

Material and methods: A selective literature search was conducted in PubMed and Google Scholar for a narrative review. Particular attention was given to larger cohort studies, systematic reviews, meta-analyses and studies on the prediction of treatment response.

Results: Chronic and treatment-resistant courses mean a relevant reduction in the quality of life and increased health risks. The assessment of treatment response is a definitional challenge: An alternative to TRD is the systemically oriented difficult to treat depression (DTD). The focus is thus moving away from symptom reduction towards controlling the level of functioning. Biomarker research for treatment response offers potential but currently mainly serves to gain theoretical knowledge.

Conclusion: Recording the long-term course of depressive illnesses is important, but also complex. Clinical interventions should therefore include a continuous monitoring and the focus on maintaining the quality of life.