[What increases the probability of manifestation in hereditary schizophrenia?]

Hereditary causes are decisive for the development of unsystematic forms of schizophrenia. In periodic catatonia a dominant, and in affective paraphrenia a recessive hereditary succession must be assumed. In cataphasia, the findings do not give any clear information about the hereditary succession. In all three forms, considerable variations of the manifestations are found. Imperative indications have been observed suggesting that the brother-and-sister constellations, which have scientifically been too much neglected, have an essential share in these phenomena. In periodic catatonia, the lack of brothers and sisters and in particular a lack of elder sisters proved to be an essential factor. Affective paraphrenics frequently are the youngest of the brothers and sisters in a family. An attempt has been made to give an explanation of these findings. Further external influences proved to be essential. In persons suffering from cataphasia, for example, the origin from rural districts and, on the other hand, the origin from a large town seem to play a role.