Understanding and explaining depression: From Karl Jaspers to Karl Friston.

The article focuses on the challenges in understanding and diagnosing major depressive disorder (MDD), highlighting the persistent gap between clinical experience and neuroscience research. It discusses the historical development of MDD as a diagnostic category, critiques of its broad and contested nature, and Karl Jaspers' distinction between understanding patients' experiences (verstehen) and explaining symptoms scientifically (erklären). The article introduces the predictive processing and active inference framework, developed by Karl Friston, which conceptualizes depression as arising from altered brain predictions and precision-weighting of interoceptive signals, linking biological, psychological, and social factors. This framework offers a potential path to bridge the explanatory gap and improve psychiatric nosology by focusing on symptom networks rather than traditional diagnostic categories.