Question
Does breastfeeding increase IQ?
Short answer
The strongest test so far suggests a modest benefit. In a randomized trial of over 17,000 infants in Belarus, children whose mothers got breastfeeding support scored about 7.5 points higher on verbal IQ at age 6.5. Full-scale IQ was about 5.9 points higher, but that result was not statistically certain.
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Why observational studies were not enough
Many studies have found that breastfed children score higher on IQ tests. But mothers who breastfeed longer tend to differ in education, income and many daily habits, so a simple comparison cannot say whether breastfeeding itself made the difference. The trial authors made exactly this point: earlier evidence was almost entirely observational and prone to confounding (Kramer et al., 2008).
The PROBIT trial
The Promotion of Breastfeeding Intervention Trial randomly assigned 31 maternity hospitals in Belarus either to a breastfeeding-support program modeled on the WHO and UNICEF Baby-Friendly Hospital Initiative or to usual care. It enrolled 17,046 healthy breastfeeding infants and followed up 13,889 of them at age 6.5 (Kramer et al., 2008).
The program worked: 43.3% of mothers in the support group were exclusively breastfeeding at 3 months, against 6.4% in the control group (Kramer et al., 2008).
Try one · Abstract Reasoning
Which tile completes the grid?
Tap the option you think is right, or show the answer.
Show the answer
The missing tile has a large outlined circle (option 1).
How to solve it
- Start with the first row and name what changes from tile to tile.
- Every row and every column contains each shape (cross, circle and star) exactly once.
- Every row and every column contains each fill (outline, hatched and solid) exactly once.
- The size (large) stays the same in every tile.
- Check the rules on the second row, then apply them to the third.
- So the missing tile has a large outlined circle.
That was 1 puzzle. The full test has 25.
The IQ results
| Measure (Wechsler Abbreviated Scale) | Difference | 95% confidence interval |
|---|---|---|
| Verbal IQ | +7.5 | +0.8 to +14.3 |
| Performance IQ | +2.9 | -3.3 to +9.1 |
| Full-scale IQ | +5.9 | -1.0 to +12.8 |
All three averages were higher in the support group, and teachers rated those children higher in reading and writing (Kramer et al., 2008). Only the verbal result had a confidence interval entirely above zero, so the full-scale gain is suggestive rather than settled. The authors concluded that prolonged and exclusive breastfeeding improves children's cognitive development.
Keeping it in proportion
A few points of average difference between groups is real but small next to the spread among children. A 15-point standard deviation means children in either group varied far more than the groups differed. For other factors with evidence behind them, see does education increase IQ and how environment shapes intelligence. For how IQ is scored in children, see the average IQ by age.
Sources
- Kramer, M. S., et al. (2008). Breastfeeding and child cognitive development: New evidence from a large randomized trial. Archives of General Psychiatry, 65(5), 578-584. doi.org/10.1001/archpsyc.65.5.578