Genetic and Environmental Factors in Psychoses of Children

Early childhood intellectual differences between schizophrenic adults and their siblings.

“…A significant difference was found despite the probability that some of the lower scoring siblings, whose scores were included in the averages, might also have developed schizophrenia later in life. In one study of psychotic children (Yerbury & Newell, 1943), half of their siblings were found also to show significant abnormality. Had it been possible to eliminate from consideration those siblings who later developed significant abnormalities, the differences found between those who became schizophrenic and their siblings undoubtedly would have been even greater.…”