Abstract

Introduction of therapeutically effective psychotropic drugs focused attention on the heterogeneity of psychiatric populations within the traditional diagnostic categories of psychiatric disorders. Recognition that valid diagnostic concepts are essential for progress in the biology and pharmacotherapy of psychiatric disorders resulted in a revival of interest in psychiatric nosology with a special emphasis on Leonhard's classification of 'endogenous psychoses'. Of particular importance for psychopharmacology in Leonhard's system is the recognition of two distinctive populations within the schizophrenic disorders, i.e., 'unsystematic schizophrenias' and 'systematic schizophrenias'; three distinctive populations within the bipolar disorders, i.e., 'manic-depressive illness,' 'cycloid psychoses' and 'unsystematic schizophrenias'; and two distinctive populations within depressive disorders, i.e., 'unipolar depression' and 'bipolar depression'. In this paper supporting data for Leonhard's classification of 'endogenous psychoses' are presented.