In the developed world, where the benefits of breastfeeding are not measured in terms of life or death or even serious morbidity, the question has been what benefits might motivate mothers to both initiate and sustain it consistent with the World Health Organization and American Academy of Pediatrics recommendations.1,2 The reduction of gastroenteritis, otitis media, and atopic eczema in the first year of life is supported by a strong evidence base.3 While these are important and desirable outcomes, none in and of themselves have dramatic public health consequences, particularly beyond early childhood. On the other hand, the connection between breastfeeding and cognition has lifelong and widespread implications. Whether a causal linkage between the two exists has long been debated, in part, because most existing studies are observational and have failed to adjust for maternal IQ. Given the known association between educational attainment or intelligence and breastfeeding, failure to adjust for maternal IQ may confound any observed effects on infants. The study by Belfort et al4 in this month’s issue of JAMA Pediatrics, although observational, has many notable strengths including controlling for maternal intelligence, as well as features of the home environment that promote cognitive function. Assuming these findings are in fact robust, what are the public health implications?