In Week 5, we looked at the Effect of breast feeding on intelligence. To assess the importance of maternal intelligence in the link between breast feeding and children's intelligence, Der et al. (2006) carried out an analysis of data from the 1979 US national longitudinal survey of youth. Data on 5475 children, the offspring of 3161 mothers in the longitudinal survey, were analysed. The main outcome measure was IQ in children. They reported that, after adjustment for maternal intelligence and other variables, the effect of breastfeeding was small (0.52 IQ scale points) and non-significant (95% confidence interval −0.19 to 1.23). They concluded that breast feeding has little or no effect on intelligence in children.
N.B. IQ has mean = 100, SD = 15, by definition.
Reference: Der G, Batty GD, Deary IJ. (2006) Effect of breast feeding on intelligence in children: prospective study, sibling pairs analysis, and meta-analysis. British Medical Journal 333, 945-948.
Question 1. What do the authors mean by adjustment for maternal intelligence?
Question 2. What method would the authors use for this adjustment and why?
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Last updated: 21 February, 2012.