Overall IQ was higher by 4 points in children who were breastfed than in those receiving formula.  Adjustments included periconception folate.  In mothers receiving Valproate (Valproic acid, Epilim) there was a mean difference of 12 IQ points between the breastfed and formula fed groups.

106 for breastfed v. 94 for formula fed P = .04

JAMA  Pediatr 2014;168. 729-736  Meador KJ et al.

A complex milk has evolved to prepare a complex human brain