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This two-volume paperbound set by the eminent Norwegian psychiatrist Einar Kringlen is a welcome addition to the nature-nurture library. Previous twin studies are reviewed thoroughly. The author's discussion of his own work is meticulous.
He believes that the psychiatrist is in "a unique position ... to bridge the gap between the biological and social sciences and present a holistic view of man." His 1964 study had shown no significant differences in concordance rates between monozygotic and dizygotic schizophrenic males. Now, all twin births registered in Norway from 1901 to 1930 have been checked against the Central Register of Psychosis, providing a larger and an unselected sample of 342 pairs of twins in which one or both have been hospitalized for schizophrenia, manicdepressive illness, or reactive psychosis. The new concordance figures for schizophrenia are 25% to 30% in monozygotic twins, and 4% to 10% in dizygotic twins.