Background
We aimed to determine the associations between breastfeeding and children’s neurodevelopment indexed by intelligence quotient (IQ) and emotional and behavioural problems through mid-childhood adjusting for prenatal and postnatal depression and multiple confounders; and to test the novel hypothesis that breastfeeding may moderate the effects of prenatal depression and anxiety on children’s neurodevelopment.

Methods
The study is based on women and their children from the longitudinal Avon Longitudinal Study of Parents and Children (n=11,096). Children’s IQ was derived from standardized in-person testing; behaviour problems were assessed according to parent-report; information on breastfeeding, prenatal depression and anxiety and multiple confounders were derived from self-report questionnaires. We conducted hierarchical multiple regression adjusting for several covariates.

Results
43% women were exclusively breastfeeding at 1 month and an additional 16.8% were engaged in mixed or partial breastfeeding. Both exclusive breastfeeding (B = 2.19; SD = 0.36, p =.00) and mixed feeding (B = 1.59; SD= 0.52; p=.00) were positively associated with IQ at 8 years of age, after adjusting for covariates. Exclusive breastfeeding was negatively associated with hyperactivity/attention deficit at 4 years (B = −.30, SD = .05; p < .01); mixed feeding was related to hyperactivity/attention deficit at age 9 (B = .20; SD = .08; p = .03) after adjustments. There was no association between breastfeeding and emotional or conduct problems. Breastfeeding did not moderate the association between prenatal depression and anxiety and children’s neurodevelopment.

Conclusions
The selective association between breastfeeding and neurodevelopmental measures suggests a nutritional rather than broader beneficial psychological effect on child neurodevelopment. Breastfeeding did not moderate the associations between prenatal depression and anxiety and child neurodevelopment, suggesting separate mechanisms of action.