Differences in Neurocognitive Development Between Children Who Had Had No Breast Milk and Those Who Had Had Breast Milk for at Least 6 Months

<b>Background</b>: There is considerable evidence that breast feeding has a beneficial effect on the neurocognition of a child. However, most studies have confined their attention to the Intelligence Quotient (IQ), tending to ignore other aspects of neurodevelopment. <b>Methodology</b>: Here we present the relationship between breast feeding for at least 6 months with 373 neurocognitive outcomes measured from infancy through to late adolescence using data collected in the Avon Longitudinal Study of Parents and Children (ALSPAC). We first examined unadjusted regression associations with breast feeding at age 6 months. Where the unadjusted <i>p</i>-value was < 0.0001 (<i>n</i> = 152 outcomes), we adjusted for social and other factors. <b>Results</b>: This resulted in 42 outcomes with adjusted associations at <i>p</i> < 0.001. Specifically, these included associations with full-scale IQ at ages 8 and 15 years (adjusted mean differences [95% confidence interval (CI)] +4.11 [95% CI 2.83, 5.39] and +5.12 [95% CI 3.57, 6.67] IQ points, respectively, compared to not breastfeeding for 6 months). As well as the components of IQ, the other phenotypes that were strongly related to breast feeding for at least 6 months were measures of academic ability (reading, use of the English language and mathematics). In accordance with the literature, we show that children who are breast fed are more likely to be right-handed. The one association that has not been recorded before concerned aspects of pragmatic speech at 9 years where the children who had been breast fed were shown to perform more appropriately. <b>Conclusions</b>: We conclude that breast feeding for at least 6 months has beneficial effects on a number of neurocognitive outcomes that are likely to play a major part in the offspring's future life course. We point out, however, the possibility that by using such stringent <i>p</i>-value criteria, other valid associations may have been ignored.