Type of dominance modification in schizophrenia

摘要

New family data on schizophrenia, gathered in Iceland, are evaluated in terms of different forms of modified dominant inheritance. In this material the risk of psychosis appears to be proportional to the likelihood of receiving a postulated major gene. Comparative rates in different groups can be adequately expressed by the formula 1.0 + 6.0(1/2)n where n represents the number of genetic steps from an affected relative. While older data on monozygotic cotwins and on children of two psychotic parents do not seem to fit this formulation, satisfactory explanations exist, so that the overall pattern of transmission appears to be consistent with dominant inheritance with incomplete penetrance. In contradistinction to this conclusion, the family data reported by other authors actually agree better with a previously proposed two locus genetic hypothesis, but in view of the improved methodology employed in the Icelandic study, the new data are felt to have greater validity.