Concordance in twins and the component partition of phenotypic variance in schizophrenia

The paper deals with a study of the pairwise and proband concordance rates to schizophrenia in 36 monozygotic (MZ) and 87 dizygotic (DZ) twins. Pairwise concordance rate to manifestative forms of schizophrenia was 0.54 and 0.18 for MZ and DZ twins, respectively, but when broader diagnostic criteria were used, the values were 0.73 and 0.27. Proband concordance rate in MZ twins was 0.70. The results of component partition of phenotypic variance show a leading role of a genotypic additive component in the development of schizophrenia (56.1%) and significance of the specific twin paratypic component. A conclusion is made on the leading role of genotypic factors in schizophrenia.