Breastfeeding and subsequent social adjustment in six- to eight-year-old children.

The relationship between breastfeeding practices and measures of conduct disorder was examined, prospectively, in a birth cohort of New Zealand children studied up to the age of eight years. While there were significant associations between the duration of breastfeeding and maternal and teacher ratings of conduct disorder obtained at six, seven and eight years, these correlations appeared largely spurious arising from the effects of errors of measurement and confounding factors which were correlated with both breastfeeding and conduct disorder measures. When errors of measurement and confounding factors were accounted for the correlations between breastfeeding and measures of conduct disorder tended to become both small and statistically non-significant. The study provides no evidence to suggest that breastfeeding makes a major contribution to the subsequent social adjustment of children.