This article has the general objective of addressing the problem of the psychosomatic that was exposed by Martin Heidegger and the Swiss psychiatrist Medard Boss in the so-called Zollikon Seminars. First, I provide an overview of the origin and gestation of these seminars, as well as their historical context. Then, the problem of method and the corresponding differentiation between psyche and soma in psychiatry are analyzed. Finally, the article collects Heidegger’s reflections on the phenomenon of the body (Leibphänomen) for making a brief analysis of Major Depressive Disorder in the DSM-5, and shows how the experience of the body (Leib) becomes an aspect fundamental to consider in the diagnosis of this type of disorder.