Monozygotic twins Twin research/studies

Twin research in schizophrenia presents us with puzzles. For example, although the usual quoted figure for concordance of schizophrenia in monozygotic (MZ) twins is approximately 50 percent, the classical modern study on the subject shows a variation of concordance of 31—58 percent depending on which Western country provides the statistics. The concordance rate in the United States, for example, is only 31 percent, while in the United Kingdom it s 58 percent.18 That is not a minor difference. 

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