Several studies have also attempted
to understand the role of breastfeeding on IQ, and although some authors conclude that the observed advantage of breastfeeding on IQ is related only
to genetic and socioenvironmental factors, a recent meta - analysis showed that after adjustment for appropriate
key co-factors, breastfeeding was associated with significantly higher scores for cognitive development than
formula feeding.6 Longer duration of breastfeeding has also been positively associated with intelligence in adulthood.22 We also observed the benefits of long - term breastfeeding on mental indices, along with the indirect benefit of balancing the impact of exposure
to p, p ′ DDE after adjustment for some socioeconomic variables.