Intended for healthcare professionals

Rapid response to:


Effect of breast feeding on intelligence in children: prospective study, sibling pairs analysis, and meta-analysis

BMJ 2006; 333 doi: (Published 02 November 2006) Cite this as: BMJ 2006;333:945

Rapid Response:

Reanalysis in light of Byelorussian trial

Since this study was completed, the results of a controlled
breastfeeding experiment on 17 046 infants was completed in Byelorussia
(Kramer, et. al., Breastfeeding and Child Cognitive Development, Archives
of General Psychiatry, May 2008). This experiment showed that encouraging
mothers to breastfeed resulted both in increased breastfeeding and in a
significant increase in infant IQ. Since this was a controlled experiment
where infants were assigned randomly to either a control group or an
intervention group, Maternal IQ could not have been a causative factor.

In light of this, the correlation between Maternal IQ, breastfeeding,
and infant IQ must be reevaluated. As none of these factors can be the
cause of both of the others, there must be some fourth causal factor.

I would suggest that the fourth, causal, factor for these three
factors is likely to be whether the mother was breastfed. People tend to
raise their own children in the same way they were themselves raised,
partly because they get advice on child rearing from their parents. It
seems likely that mothers who were breastfed are much more likely to
breastfeed their own infants. In conjunction with the now proven effect
of breastfeeding on IQ, breastfeeding of the mother explains all the of
the other factors: mother's IQ, breastfeeding of the infant, and infant's

Competing interests:
None declared

Competing interests: No competing interests

07 August 2009
Warren J Dew