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The causal effect of breastfeeding on children’s cognitive development : a quasi-experimental design
Author(s)
Date Issued
2010-03
Date Available
2010-12-06T16:48:57Z
Abstract
Objective: To estimate the causal effect of breastfeeding on children’s cognitive skills as
measured at ages 3, 5, 7 and 11.
Design: An instrumental variable (IV) strategy which provides a correction method for
dealing with selection bias. Standard linear regression models are compared to two-stage
least squares models to test for the presence of endogeneity. The consistency of the results
across multiple sources is also tested using data from two prospective longitudinal studies
collected 40-years apart.
Setting: The 1958 National Child Development Study (NCDS) and the 2000 UK Millennium
Cohort Study (MCS).
Participants: Data on 11,792 (age 3) and 9117 (age 5) children in MCS and 4923 (age 7 and
11) children in NCDS.
Main outcome measures: Cognitive ability is measured by the Bracken School Readiness
Assessment (age 3); Foundation Stage Profile (age 5); and tests of general ability including
mathematics, comprehension, verbal and non-verbal skills (ages 7 and 11).
Results: The duration of breastfeeding has a small, but significant, effect on children’s
cognitive skills in the linear regression models at ages 3, 5, 7 and 11, but no effect in the IV
models. However, in all cases, the hypothesis that breastfeeding is endogenous is rejected,
indicating that the results of the linear regressions are valid.
Conclusion: The relationship between breastfeeding and cognitive ability is not driven by
selection bias once a rich set of confounders are included. IV methods can therefore be used
to test for the presence of selection bias and are a useful alternative for identifying causal
relationships when randomised control trials are not feasible. Showing that the size of the
effect is similar for two cohorts born over 40 years apart, and using different measures of
ability, are further indications that the relationship between breastfeeding and cognitive
ability is not a statistical artefact.
Sponsorship
Not applicable
Type of Material
Working Paper
Publisher
University College Dublin. School of Economics
University College Dublin. Geary Institute
Series
UCD Centre for Economic Research Working Paper Series
Wp 10 05
UCD Geary Institute Discussion Paper Series
WP2010/20
Subject – LCSH
Breast Feeding
Child Development
Cognition in children
Web versions
Language
English
Status of Item
Not peer reviewed
This item is made available under a Creative Commons License
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