Norwegian study: longer exclusive breastfeeding linked to fewer ADHD symptoms at ages 3, 5 and 8
An observational Norwegian study links each extra month of exclusive breastfeeding to fewer parent-rated ADHD symptoms in childhood; the authors note the effect per child is small.
A team led by Berit Skretting Solberg, a visiting researcher at the University of Bergen in Norway, reports that children who were exclusively breastfed for longer showed fewer ADHD symptoms in childhood. The study was published in Biological Psychiatry and covered by gigazine.net. gigazine.net
gigazine.netgigazine.netOpen source ↗ The researchers analysed data from Norwegian families followed from pregnancy through early childhood.
Exclusive breastfeeding was defined as giving breast milk only, with no formula and no solid food. The WHO recommends it up to 6 months of age. Earlier studies linked breastfeeding in infancy to a lower chance of a later ADHD diagnosis, but it was hard to tell whether breastfeeding itself or lifestyle was responsible. Mothers who can continue breastfeeding may differ in socioeconomic status, and maternal ADHD may make breastfeeding harder while also raising the child's genetic risk.
Design and main result
The first analysis covered children born in 1999–2009. Mothers answered a questionnaire on breastfeeding when the child was 6 months old. Parents then rated hyperactivity, impulsivity and inattention when the child was 3, 5 and 8 years old. The team also mapped the children's genetic profiles and calculated a genetic risk score for ADHD. Each additional month of exclusive breastfeeding was associated with fewer symptoms at all three ages.
In a second group of parent–child pairs, the statistical models were adjusted for parental genetic risk scores, the child's genetic data, maternal education, parental age at birth, birth weight, season of birth and socioeconomic factors. The trend held: a shorter period of exclusive breastfeeding, or feeding that included more than breast milk, was consistently linked to more symptoms. gigazine.net
gigazine.netgigazine.netOpen source ↗
Siblings and limits
The researchers then examined more than 5000 sibling pairs whose periods of exclusive breastfeeding differed. Longer breastfeeding again went with fewer symptoms. According to the authors, this suggests that milk or the act of nursing itself may influence behavioural development biologically and psychologically, even when genetic, socioeconomic and environmental factors are the same.
The reduction in symptoms was small at the level of an individual child. The authors note that exclusive breastfeeding does not necessarily produce a clinically significant change in a particular child. Further work is needed on the biological mechanisms by which breastfeeding may affect the developing brain, including nutrients in milk and skin-to-skin contact during feeding.
