[The origin of cycloid psychoses].

Hereditary affliction with psychosis is not a marked phenomenon in cycloid psychoses, it is, however, found that parents may promote the outbreak of the disease by their abnormal behaviour. Of greater importance are causes which--unlike other forms of endogenic psychosis--develop their effect in infancy. Inharmonious constellations among brothers and sisters have been found to be essential. It has been proved that in the physiological and psychic development of man the mutual influence of children plays an important role. Paying more attention to the influence exerted by the parents, especially the mother, this law has been overlooked until now. The constellations of brothers and sisters, which are of course an everyday phenomenon, are not effective in themselves, but will only become effective when they coincide in a specific manner with temperaments that in their nature show a certain relationship with psychoses. On the other hand, physical influences do exist in a form that is found in no other type of the so-called endogenous psychoses. As regards their quite peculiar genesis, the demarkation of the cycloid psychoses from the unsystematic forms of schizophrenia, which are mainly hereditary, is indispensable. In the term "schizo-affective psychoses" of the WHO the two forms are unfortunately mixed up.