Historical aspects of the dichotomy between manic-depressive disorders and schizophrenia

The history of psychiatric classification is highly complex and this presentation must be restricted to a simplified overview. Guislain [Guislain, J., 1833. Traité des phrénopathies ou doctrine nouvelle des maladies mentales. Etablissement Encyclopédique, Brussels] and Zeller [Beil. Med. Corresp.-Bl. Würtemb. Arztl. Ver. 7 (1837) 321] established a unitarian concept of psychiatric disorder, permutations of which have survived until the present day. Kraepelin's [Kraepelin, E., 1899. Psychiatrie. Ein Lehrbuch für Studierende und Arzte (6th edn.). Johann Ambrosius Barth, Leipzig] dichotomy between "manic-depressive insanity" and dementia praecox was built mainly on Kahlbaum's [Kahlbaum, K., 1863. Die Gruppirung der Psychischen Krankheiten und die Eintheilung der Seelenstörungen. AW Kafemann, Danzig] classification, which took clinical symptoms, course and outcome into account. Kraepelin's well-accepted approach sought to provide a basis for diagnosis, prognosis, choice of treatment and causal research. Kraepelin's dichotomy came to be questioned on several grounds: (1) doubts about his unification of bipolar disorder [Gaz. Hôp. 24 (1851) 18] with melancholia, (2) doubts about the significance of Kraepelin's diagnostic groups for causal research [Z. Gesamte Neurol. Psychiatr. 12 (1912) 540], illustrated best by the work of Bonhoeffer [Bonhoefferm, K., 1912. Die symptomatischen Psychosen im Gefolge akuter Infektionen, Allgemeinerkrankungen und innerer Krankheiten. In: Aschaffenburg, G. (Ed.), Handbuch der Psychiatrie, 3. Abt., 1. Hälfte. Deuticke, Leipzig Wien], (3) the complex psychopathological descriptions and classifications of numerous subgroups of psychoses by Kleist [Monatsschr. Psychiatr. Neurol. 125 (1953) 526] and Leonhard [Leonhard, K., 1968. Aufteilung der endogenen Psychosen (4th edn.). Akademie Verlag, Berlin] and (4) description of the psychoses between affective and schizophrenic disorders (intermediate psychoses, mixed psychoses, schizo-affective psychoses) beginning with Kehrer and Kretschmer [Kehrer, F., Kretschmer, E., 1924. Die Veranlagung zu seelischen Störungen. (Monographien aus dem Gesamtgebiete der Neurologie 40) Springer, Berlin] and persisting up to the modern findings of a continuum between the two major groups of psychiatric disorders. Kraepelin's simplification has so far been more successful than the Kleist-Leonhard approach, but the modern and more descriptive trend in psychiatric classification favours the syndromal concept of Hoche and the concepts of continua between affective and schizophrenic disorders and between normal and pathological behaviour.