Twin Research and Human Genetics

Articles

No Evidence of Genetic Mediation in the Association Between Birthweight and Academic Performance in 2,413 Danish Adolescent Twin Pairs

Inge Petersena1 c1, Vibeke Myrup Jensena2, Matt McGuea3, Paul Bingleya4 and Kaare Christensena5

a1 The Danish Twin Registry, Epidemiology, University of Southern Denmark, Denmark. IPetersen@health.sdu.dk

a2 Department of Economics, Aarhus School of Business, Aarhus University, Denmark; The Danish National Centre for Social Research, Denmark.

a3 The Danish Twin Registry, Epidemiology, University of Southern Denmark, Denmark; Department of Psychology, University of Minnesota, United States of America.

a4 The Danish National Centre for Social Research, Denmark.

a5 The Danish Twin Registry, Epidemiology, University of Southern Denmark, Denmark.

Abstract

Evidence of a positive association between birthweight and IQ has been established in several studies. Analyses of within twin pair differences in birthweight and IQ have been used to shed light on the basis of the association. The strength of this approach is the possibility of controlling for both unmeasured common childhood–environmental factors as well as genetic factors shared by the co-twins. Two twin studies suggest the existence of genetic mediation between birthweight and IQ, that is, common genetic factors influence both fetal growth and IQ in childhood, while two other twin studies find no evidence of such mediation. In the present study we use a large population-based national register study of 2,413 Danish twin-pairs from birth cohorts 1986–1990, of which we have zygosity information on 74%. We perform individual level as well as intra-pair analyses of birthweight and school achievements at age 16. For both sexes we observed a monotonic increase in academic performance with increasing percentiles of birthweight. However, we did not find that this association is due to genetic mediation.

(Received May 13 2009)

(Accepted August 01 2009)

Keywords

  • twins;
  • academic performance;
  • genetic mediation;
  • birthweight

Correspondence:

c1 Address for correspondence: Inge Petersen, The Danish Twin Registry, Epidemiology, University of Southern Denmark, 5000 Odense C, Denmark.

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