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Table 19.2Twin studies in schizophrenia

StudyConcordant MZ pairsConcordant DZ pairs
Kringlen, 196814/55 (21/55)4–10%
Fischer et al., 1969 5/21 (10/21)10–19%
Tienari, 19753/20 (5/16)3/42
Farmer, 19876/16 (10/20)1/21 (4/31)
Onstad et al., 1991 8/241/28

The numbers show pairwise concordances, i.e. counts of the number of concordant (+/+) and discordant (+/-) pairs ascertained through an affected proband. Concordances can also be calculated probandwise, counting a pair twice if both were probands. This gives higher values for the MZ concordance. Probandwise concordances are thought to be more comparable with other measures of family clustering. Only the studies of Onstad and Farmer use the current standard diagnostic criteria, DSM-III. Figures in brackets are obtained using a wider definition of affected, including borderline phenotypes. For all references, see Fischer et al. (1969) and Onstad et al. (1991).

From: Chapter 19, Complex diseases: theory and results

Cover of Human Molecular Genetics
Human Molecular Genetics. 2nd edition.
Strachan T, Read AP.
New York: Wiley-Liss; 1999.
Copyright © 1999, Garland Science.

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