There are several studies ( https://lacted.org/questions/0230-breastfeeding-child-iq/) demonstrating that formula fed infants have a higher risk of lower IQ. The association between infant feeding and cognition exists for both premature and term infants.
A 2022 Australian prospective study of 586 infants born <33 weeks gestation found that maternal milk feeding during the NICU stay and after discharge was associated with improved school-age performance IQ and academic achievement at 7 years of age.
The study reviewed for today’s question was done in China, where the authors report having the second greatest number of preterm births in the world. Among these preterm infants, 60.6% have cerebral palsy, 55% have learning disabilities upon entering school, and 20% need special education. Knowing the association between infant feeding and cognitive development, the researchers evaluated brain gray matter structure and function using MRI technology to detect differences based on infant feeding.
Thirty-four breastmilk-fed infants and 22 formula fed infants, all born ~ 32 weeks gestation, underwent brain MRIs at 40 weeks corrected (2 months after birth), after sedation with chloral hydrate.
They found that the formula fed infants had less activation of the R superior temporal gyrus as compared to the breastmilk fed infants. The formula fed infants had less gray matter volume in the bilateral frontal lobe, L caudate nucleus and R temporal lobe as compared to the breastmilk fed infants.