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August 21, 2002

Breastfeeding and Later Intelligence—Reply

Author Affiliations

Stephen J.LurieMD, PhD, Senior EditorIndividualAuthor

JAMA. 2002;288(7):828-830. doi:10.1001/jama.288.7.828

In Reply: In response to Dr Weissman and Ms Weissman, we pointed out that duration of breastfeeding may be an indicator of the interest, time, and energy that the mother is able to invest in the child. We concluded that not only nutrients in breast milk but also behavioral factors and factors associated with the choice of feeding method may contribute to the positive association between duration of breastfeeding and adult intelligence. Maternal depression, alcohol abuse, and quality of marital relationship may be among the many factors affecting not only duration of breastfeeding but also many other aspects of the family environment. Maternal depression may relate to single mother status and alcohol use may relate to smoking, but both single mother status and smoking were included as covariates in our analysis (in 1960, alcohol consumption among Danish women was so rare that it was not among the several hundred variables registered by Zachau-Christiansen1). Maternal depression may be associated with low intelligence in offspring, but a recent study that controlled both maternal IQ and depression (assessed at 3 months) still found a significant association between breastfeeding and intellectual ability at 11 years of age.2 Furthermore, in our study 28% of the WAIS (Wechsler Adult Intelligence Scale) sample was breastfed for less than 1 month and 59% for 3 months or less. The great majority of these mothers must have been mentally healthy, and consequently it is unlikely that maternal depression can explain the significant association between duration of breastfeeding and offspring intelligence.