• We studied the incidence of psychopathologic disorder in offspring of monozygotic twins discordant for schizophrenia. The original material was based on a complete national sample of twins who were hospitalized for functional psychosis in Norway. A comparison of adult offspring of schizophrenic monozygotic twins with offspring of their nonpsychotic cotwins showed that although there are more schizophrenic and schizophreniclike cases in the first group, an observation that may be ascribed to environmental factors, the difference is not statistically significant.
Kringlen E, Cramer G. Offspring of Monozygotic Twins Discordant for Schizophrenia. Arch Gen Psychiatry. 1989;46(10):873-877. doi:10.1001/archpsyc.1989.01810100015003