Schizophrenia is a relatively common familial disorder that has been the subject of numerous family, twin, and adoption studies. Despite the large amount of family data available, there is no consensus among geneticists about the mode of inheritance for the disorder. The methods that have been used in the analysis of schizophrenia family data are described and their results summarized. It is concluded that both genetic and environmental factors contribute to the liability for developing schizophrenia. Environmental factors are more likely to be nonfamilial than familial. Genetic effects upon schizophrenia liability are consistent with either a multifactorial or a mixed multifactorial single-gene model of transmission; a single-major-gene model, however, is not consistent with the family data. Although major-gene effects upon schizophrenia are possible, it appears that the identification of such effects will be difficult unless a multivariate approach to segregation analysis is taken.
- path analysis
- segregation analysis