In a study published in the May 8, 2002, Journal of the American Medical Association (JAMA), researchers found that infants breastfed for seven to nine months had higher IQs as adults than those breastfed less than seven months.
In a study published in the May 8, 2002, Journal of the American Medical Association (JAMA), researchers found that infants breastfed for seven to nine months had higher IQs as adults than those breastfed less than seven months.

Using two types of intelligence tests, researchers compared IQ scores for young adults who had been breastfed for various lengths of time. While the study showed an increase in intelligence at all duration levels of breastfeeding, participants who had been breastfed for seven to nine months showed the largest increase of IQ points at six, compared to those breastfed for one month or less.

Using a two-pronged approach to evaluate more than 3,000 young adults in Copenhagen, Denmark, researchers took into account other factors that might contribute to the IQ increase such as parental social status and education; single mother status; mother's height, age and weight gain during pregnancy, and cigarette consumption during the third trimester as well as number of pregnancies; estimated gestational age; birth weight; birth length; and indexes of pregnancy and delivery complications. The scientists concluded that duration of breastfeeding may have long-term positive effects on cognitive and intellectual development.

While previous studies have demonstrated a positive relationship between breastfeeding and psychomotor and mental development in children, most of them stressed the significant difference between those infants who had been breastfed versus those who were fed artificial baby milk. This study is unique in that it demonstrates the positive, life-long effects of breastfeeding by testing young adults in relationship to the duration of their breastfeeding experience as infants and because it is the first to track IQ into maturity. Scientists believe that the nutrients in human milk, maternal behavior, and factors associated with the choice of feeding method all play a part in the positive correlation between duration of breastfeeding and increased IQ.

Previous research has well documented additional long-term positive effects of breastfeeding both for the baby and the mother. For the infant, long-term effects of breastfeeding include reduced risk of celiac disease, diabetes, obesity, some childhood cancers, Crohn's disease, urinary tract infections, atopic disease and reduced endometriosis in women in later life. For the breastfeeding mother, there is reduced risk of breast cancer, ovarian cancer and osteoporosis
Source: La Leche League International