In 209 families with schizophrenic children, 18 families with more than one abnormal child were found. Among the parents of this group there was a high incidence of marital discord, schizoid personalities and different forms of schizophrenia. Among the siblings mental defect, speech delay, and schizophrenia were found. Because of the high incidence of the children in this group functioning on a mentally defective level, special attention was paid to the problem of the intellectual function of all family members. Twenty-four (40%) of the 60 children in these 18 families studied presented a picture of intellectual defects along with schizophrenic process. In three (5%) mental defect was found without typical symptoms of childhood schizophrenia. None of the parents were found to be mentally defective and only one was found to be of borderline intelligence. Twenty (55%) parents were of normal intelligence and 15 (42%) were bright normal to superior, while the corresponding figures for the children were 22 (36.6%) and six (10%). There were only four children whose intellectual function improved while there were 16 who deteriorated considerably. There was an unexplained finding of an unusually high number of twins among the 18 families. We found five pairs of twins. Two pairs were monozygotic, concordant for schizophrenia. Two pairs were dizygotic, discordant for schizophrenia. One of the fifth pair died early; the second was mentally defective.
