[Classification of depression].

The results of recent research indicate that the traditional subdivision of depressive disorders into a "biological" ("endogenous") and a "psychosocial" ("neurotic") type cannot be upheld in this simple categorical form today. This is demonstrated by referring to such new developments as the construction of international compromise classification systems, the formulation of operational research diagnosis criteria, attempts at validating diagnostic formulations by external variables (such as biological markers) and the introduction of multiaxial diagnostic systems. The use of a "polydiagnostic" approach to psychiatric research is recommended, i.e. to use several diagnostic formulations for subtyping depression simultaneously in psychiatric research. It is anticipated that by applying the "polydiagnostic" approach the growing uncertainty and confusion in the subclassification of depression can be reduced.