[Physiopathogeny in psychiatry: discovery, construction or discovery plus construction? The "case" of depression]

This work summarizes the efforts made in the last twenty years towards the discovery of the physiopathogeny of mental diseases. It takes the "case" of major depression and reviews the different theories proposed to explain its physiopathogeny beginning with the role of excitatory aminoacids, glucocorticoids and trophic neurofactors in the '90s, the neurogenesis at the beginning of '00s and the genetics, the epigenetics and the research on neural networks in the last years. Result of these scientific efforts seem to be a construction which has at the same time the strength of the evidences employed in its building and the weakness that emerges from the reductionism necessary to obtain them.