Twin Research
- Twin Research / Volume 2 / Issue 04 / August 1999, pp 244-249
- Copyright © Cambridge University Press 1999
- DOI: http://dx.doi.org/10.1375/twin.2.4.244 (About DOI), Published online: 21 February 2012
Articles
Chorion type as a possible influence on the results and interpretation of twin study data
Carol A Prescotta1 c1, Ronald C Johnsona2 and John J McArdlea3
a1 Virginia Institute for Psychiatric and Behavioral Genetics, Department of Psychiatry, Virginia Commonwealth University, Richmond, VA, USA. cprescott@hsc.vcu.edu
a2 Departments of Psychology and Psychiatry, University of Hawaii, Honolulu, HI, USA.
a3 Department of Psychology, University of Virginia, Charlottesville, VA, USA.
Abstract
The estimation of genetic effects from twin studies usually relies upon the equal environment assumption — that monozygous (MZ) and dizygous (DZ) twin pairs experience equal similarity of their environments from prenatal experiences through adulthood. However, the sharing of a chorion may make a subset of identical twins more similar, or in some cases, more different, than twins that do not share a chorion. Recent studies suggest monochorionic MZ twins resemble one another more than dichorionic MZ twins in cognitive abilities, personality, and risk for psychiatric disorder. To the extent that prenatal environment affects these characteristics, the traditional twin method will yield biased estimates of genetic and environmental influences. We develop models for quantifying this bias and estimating the influence of chorion type on estimates of heritability.
(Received October 20 1998)
(Accepted October 26 1998)
Keywords
- genetics;
- methodology;
- maternal influences
Correspondence:
c1 Correspondence: Dr CA Prescott, Virginia Institute for Psychiatric and Behavioral Genetics, Department of Psychiatry, PO Box 980126, Virginia Commonwealth University, Richmond, VA 23298, USA. Tel: (804) 828 5968; Fax: (804) 828 1471;
