A study published in the May issue of the Archives of General Psychiatry adds to the body of evidence showing that breastfeeding improves IQ. According to lead author, Michael S. Kramer, M.D., exclusive breastfeeding for at least 3 months and prolonged breastfeeding for at least 1 year makes kids smarter.

Prior studies found an association between breastfeeding and IQ, but most of the studies were observation studies in which the sample was self-selected—children of mothers who choose to breastfeed were compared with children whose mothers chose not to breastfeed. Because mothers who choose to breastfeed may interact with their children in a different way, there is no way to insure that the differences in IQ are due to breastfeeding.

Cluster-randomized trial
In contrast, the large-scale study by Kramer and colleagues included nearly 14,000 mother/child pairs. Mothers and children were randomly assigned to one of two groups: one group of mothers (the control group) received routine maternity care and the other group (the intervention group) received breastfeeding encouragement and support modeled after the World Health Organization’s Ten Steps to Successful Breastfeeding.

Forty-three percent of mothers in the intervention group breastfed exclusively for 3 months compared to 6 percent in the control group. Intelligence tests were administered to the children at age six and one-half years. Children in the intervention group had verbal IQ scores that were 7.5 points higher, nonverbal IQ scores that were 2.9 points higher, and overall intelligence scores that were 5.9 points higher.

Are the small differences in IQ significant?
The significance of 6 points is debatable. Dr. Arthur Jensen in his book titled, Straight Talk about Mental Tests, cites the following four IQ thresholds:

• 50 or below. This is the threshold below which most adults cannot cope outside of an institution. They can typically be taught to read at a 3rd or 4th grade level. However, they cannot normally function in the customary classroom setting, and they require special training programs.

• 50 and 75. At this level of intelligence, they generally cannot complete elementary school. Most adults will need help in coping with the world.

• 75 and 105. Children in this IQ range are not generally able to complete a college preparatory course in high school.

• 105 and 115. May graduate from college but generally, not with grades that would qualify them for graduate school.

• 115 or higher. No restrictions.

Depending on your child’s IQ potential, six points may make a difference.