Abstract
In this study we have compared selected aspects of the early life history of ninety-eight schizophrenic patients with those of a sibling of the same sex.
As a group the patients were lower in educational attainment, were more frequently first employed in unskilled labour, and were married less frequently than their siblings. Since these were differences between members of the same family, they suggest that the basic intelligence and/or personality of the individual contributes to the development of schizophrenia over and above the environment in which he is reared. Since the inferiority of the patients' education and first occupation refer to a period of life before the onset of the psychosis, they suggest a primary defect rather than simply a downward social drift of the sick individual.