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What Causes What
SMOKE+ INCREASES

Breastfeeding duration → Cognitive performance

Higher Breastfeeding duration increases Cognitive performance.

In three European birth cohorts, longer breastfeeding tracked with higher child IQ on crude models. After maternal IQ, education, and class, Generation R's 0.32 IQ points per month fell to 0.09 and crossed zero. Sabadell's full breastfeeding past six months still sat 7.4 McCarthy points higher. Nobody randomized the feed.

Observational · Low · N=3761

The association disappears when you account for other factors, like socioeconomic status or healthy-user bias.

Mechanism

Authors usually name long-chain fats in milk, especially DHA, plus fewer infections and more talk time with the child. Sajjad followed 3,761 Generation R children to a non-verbal IQ test at age 6. Each extra month of breastfeeding looked like 0.32 IQ points (0.20 to 0.44) before family variables. After child factors, parents' lifestyles, sociodemographics, and maternal IQ, the slope was 0.09 (-0.03 to 0.21). The authors say they cannot confirm a benefit. Julvez assessed 434 INMA children in Sabadell with the McCarthy scales at 4. Full breastfeeding longer than six months still sat 7.4 points above never (2.8 to 12.0) after social class, education, maternal IQ, psychopathology, and colostrum omega-3. The fatty acids themselves were not associated with the scores. Bernard measured colostrum PUFA and WPPSI-III at 5 to 6 in 1,080 EDEN children. Ever versus never breastfeeding was 4.5 full-scale points unadjusted and 1.3 after adjustment (-0.4 to 3.0). Duration still tracked full-scale IQ at 0.20 points per month (0.00 to 0.41) and verbal IQ at 0.31 (0.09 to 0.52). High linoleic acid with low DHA sat lower than high-DHA colostrum. The open backdoor is who breastfeeds. Mothers with more schooling and higher IQ do it longer. That path also predicts the child's test.

Caveats

The stamp is smoke because these are birth-cohort observations. A new observational edge publishes as spurious and low. Paper count does not raise it. Nobody assigned breastfeeding at random. Generation R is the largest file and the one that measured maternal IQ. Adjustment killed the association. EDEN's ever-versus-never contrast died the same way. INMA kept a long-full-breastfeeding contrast after those covariates. That disagreement is why confidence stays low. The tests are different: non-verbal IQ at 6, McCarthy at 4, WPPSI-III at 5 to 6. Full breastfeeding is not the same as any breastfeeding. Colostrum PUFA is a milk chemistry reading, not the duration node. This page is not antiepileptic drugs in milk and not diet quality in children born very low birth weight. This is not medical advice and not a recommendation to feed a certain number of months.

Effect

beta = 0.09. Sajjad Generation R: +0.32 IQ/month crude, +0.09 (-0.03 to 0.21) after maternal IQ and SES. Julvez INMA >6mo full BF +7.4 MSCA. Bernard EDEN duration +0.20 FSIQ/month.

Nodes

Lifestyle & environmentBreastfeeding durationPsychology & behaviorCognitive performance

Named confounders

Cite this page

What Causes What. “Breastfeeding duration → Cognitive performance.” https://whatcauseswhat.org/edges/e-breastfeeding-cognition (atlas updated 2026-09-02).

https://whatcauseswhat.org/edges/e-breastfeeding-cognition

Papers