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Improved estimates of the benefits of breastfeeding using sibling comparisons to reduce selection bias


  • Reilly, Siobhan
  • Evenhouse, Eirik


Objective Better measurement of the health and cognitive benefits of breastfeeding by using sibling comparisons to reduce sample selection bias. Data We use data on the breastfeeding history, physical and emotional health, academic performance, cognitive ability, and demographic characteristics of 16,903 adolescents from the first (1994) wave of the National Longitudinal Study of Adolescent Health. The sample includes 2,734 sibling pairs. Study Design We examine the relationship between breastfeeding history and 15 indicators of physical health, emotional health, and cognitive ability, using ordinary least squares and logit regression. For each indicator, we estimate, in addition to the usual between-family model, a within-family model to see whether differences in siblings' outcomes are associated with differences in the siblings' breastfeeding histories. Principal Findings. Nearly all of the correlations found in the between-family model become statistically insignificant in the within-family model. The notable exception is a persistent positive correlation between breastfeeding and cognitive ability. These findings hold whether breastfeeding is measured in terms of duration or as a Yes/No variable. Conclusions This study provides persuasive evidence of a causal connection between breastfeeding and intelligence. However, it also suggests that nonexperimental studies of breastfeeding overstate some of its other long-term benefits, even if controls are included for race, ethnicity, income, and education. The definitive version is available at

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  • Reilly, Siobhan & Evenhouse, Eirik, 2005. "Improved estimates of the benefits of breastfeeding using sibling comparisons to reduce selection bias," MPRA Paper 13434, University Library of Munich, Germany.
  • Handle: RePEc:pra:mprapa:13434

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    References listed on IDEAS

    1. Griliches, Zvi, 1979. "Sibling Models and Data in Economics: Beginnings of a Survey," Journal of Political Economy, University of Chicago Press, vol. 87(5), pages 37-64, October.
    2. repec:aph:ajpbhl:1995:85:5:729-731_1 is not listed on IDEAS
    3. Card, David, 1999. "The causal effect of education on earnings," Handbook of Labor Economics,in: O. Ashenfelter & D. Card (ed.), Handbook of Labor Economics, edition 1, volume 3, chapter 30, pages 1801-1863 Elsevier.
    4. Anderson, Patricia M. & Butcher, Kristin F. & Levine, Phillip B., 2003. "Maternal employment and overweight children," Journal of Health Economics, Elsevier, vol. 22(3), pages 477-504, May.
    5. Behrman, Jere R & Rosenzweig, Mark R & Taubman, Paul, 1994. "Endowments and the Allocation of Schooling in the Family and in the Marriage Market: The Twins Experiment," Journal of Political Economy, University of Chicago Press, vol. 102(6), pages 1131-1174, December.
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    Cited by:

    1. George Wehby, 2014. "Breastfeeding and Child Disability: A Comparison of Siblings from the United States," NBER Working Papers 19940, National Bureau of Economic Research, Inc.
    2. Kieron J. Barclay & Martin Kolk, 2017. "The Long-Term Cognitive and Socioeconomic Consequences of Birth Intervals: A Within-Family Sibling Comparison Using Swedish Register Data," Demography, Springer;Population Association of America (PAA), vol. 54(2), pages 459-484, April.
    3. Emla Fitzsimons & Marcos Vera-Hernandez, 2013. "Food for Thought? Breastfeeding and Child Development," IFS Working Papers W13/31, Institute for Fiscal Studies.
    4. Kevin Denny & Orla Doyle, 2010. "The causal effect of breastfeeding on children’s cognitive development : a quasi-experimental design," Working Papers 201005, School of Economics, University College Dublin.
    5. McCrory, Cathal & Layte, Richard, 2011. "The effect of breastfeeding on children's educational test scores at nine years of age: Results of an Irish cohort study," Social Science & Medicine, Elsevier, vol. 72(9), pages 1515-1521, May.
    6. Resul Cesur & Joseph J. Sabia & Inas Rashad Kelly & Muzhe Yang, 2017. "The effect of breastfeeding on young adult wages: new evidence from the add health," Review of Economics of the Household, Springer, vol. 15(1), pages 25-51, March.
    7. Borra, Cristina & Iacovou, Maria & Sevilla, Almudena, 2012. "The effect of breastfeeding on children's cognitive and noncognitive development," Labour Economics, Elsevier, vol. 19(4), pages 496-515.
    8. Colen, Cynthia G. & Ramey, David M., 2014. "Is breast truly best? Estimating the effects of breastfeeding on long-term child health and wellbeing in the United States using sibling comparisons," Social Science & Medicine, Elsevier, vol. 109(C), pages 55-65.
    9. Wehby, George L., 2014. "Breastfeeding and child disability: A comparison of siblings from the United States," Economics & Human Biology, Elsevier, vol. 15(C), pages 13-22.
    10. Daniel I. Rees & Joseph J. Sabia, 2009. "The Effect of Breast Feeding on Educational Attainment: Evidence from Sibling Data," Journal of Human Capital, University of Chicago Press, vol. 3(1), pages 43-72.
    11. Del Bono, Emilia & Rabe, Birgitta, 2012. "Breastfeeding and child cognitive outcomes: evidence from a hospital-based breastfeeding support policy," ISER Working Paper Series 2012-29, Institute for Social and Economic Research.

    More about this item


    Breast feeding; siblings; adolescents; intelligence; obesity; BMI; selection bias; breastfeeding; academic performance; allergy; PVT; Add Health; National Longitudinal Survey of Adolescent Health; bonding; overweight; diabetes; IQ; asthma; depression; human capital; parental investment; school failure;

    JEL classification:

    • J13 - Labor and Demographic Economics - - Demographic Economics - - - Fertility; Family Planning; Child Care; Children; Youth
    • I12 - Health, Education, and Welfare - - Health - - - Health Behavior
    • D1 - Microeconomics - - Household Behavior


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