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Heritability Estimates from Twin Studies: The Efficiency of the MZA Design

Published online by Cambridge University Press:  24 October 2025

David T. Lykken ,
Seymour Geisser  and
Auke Tellegen
David T. Lykken
Affiliation:
Departments of Psychiatry and Psychology, University of Minnesota, Minneapolis, Minnesota, USA
Seymour Geisser
Affiliation:
Department of Statistics, University of Minnesota, Minneapolis, Minnesota, USA
Auke Tellegen
Affiliation:
Department of Psychology, University of Minnesota, Minneapolis, Minnesota, USA
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Abstract

The most accurate confidence intervals for estimates of heritability are based on Fisher’s Z-transformation. Using these methods, Loehlin and Nichol’s (1976) analysis is confirmed, viz., that it is pointless to estimate heritabilities from the classical twin method unless one is prepared to recruit upwards of 800 twin pairs for study. Even then the assumptions of that method are so improbable as to leave reasonable doubt about the true value of H. Estimates of H from the correlation of monozygotic twins reared apart (MZA twins), on the other hand, is remarkably more stable than that obtained by comparing MZ with DZ correlations. Moreover, estimates of H based on the MZA design rest upon more reasonable (and often testable) assumptions.

Keywords

HeritabilityIntraclass correlationTwinsConfidence intervalsMZA twins

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Type
Article
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Twin Research and Human Genetics , First View , pp. 1 - 5
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Copyright
© International Society for Twins Studies, 2025. Published by Cambridge University Press on behalf of International Society for Twin Studies

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Footnotes

*

An explanation of the circumstances of this publication can be found in the accompanying appendix, ‘Our Colleagues’ Unpublished Manuscript: A Gift to Current and Future Investigators’ by Thomas J. Bouchard, Jr., Nancy L. Segal, and Matt McGue.

References

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