[Hereditary and psychosocial causes of schizophrenia]

On the basis of the examination of patients with endogenic psychosis, indications were obtained that there are forms that mainly develop on a hereditary basis, and forms determined by psychosocial causes. In unsystematic schizophrenia the chief factors are hereditary, above all in periodic catatonia. On the other hand, there are a few indications of a hereditary genesis in systematic schizophrenia although it is just these forms that are distinguished by the severity of their course. By studying twins, cases of schizophrenia in infancy, and the circumstances of brothers and sisters, strong indications of psychosocial causes of systematic schizophrenia were found. Lack of contacts in the course of development appears to the determing factor. In motility psychosis, one of the cycloid psychoses, indications were found that excessive encouragement by other children can be a cause of overstrain and thus may be detrimental. The conclusions drawn are based on concrete findings obtained in a total of 1,114 cases and are for the most part statistically significant.