Children who received full breastfeeding for the first six months of life tended to show fewer symptoms of attention deficit hyperactivity disorder (ADHD) during childhood, according to a large-scale Norwegian study published in the scientific journal Biological Psychiatry. The researchers found the link held even after accounting for the child's and parents' genetic background, family characteristics, socioeconomic status, and other factors that could influence disorder development.

The study drew on data from 37,643 children born in Norway between 1999 and 2009. Researchers tracked them at ages three, five, and eight, examining the relationship between breastfeeding duration and ADHD symptoms. They also analyzed data from more than 18,000 families with available genetic information on the mother, father, and child to test whether genetics alone could explain the results.

"It is well known that both genetic and environmental factors influence the development of psychiatric disorders," said Dr. Britt Skretting Solberg, a psychiatrist and researcher at the University of Bergen. "We found that the longer the child was fully breastfed up to age six months, the fewer ADHD symptoms appeared at ages three, five, and eight."

Researchers noted that partial breastfeeding was also associated with fewer ADHD symptoms, though the strongest connection appeared among children who received full breastfeeding for six months. Longer durations of full breastfeeding correlated with even greater reductions in attention deficit symptoms, a pattern described as a "dose-response" relationship.

One central question is whether the link stems from breastfeeding itself or from differences in mothers who breastfeed longer, which might affect child development in other ways.

To minimize such influences, researchers adjusted statistically for many variables including parental age, maternal education level, birth weight, gestational age, number of prior births, birth season, and socioeconomic factors. They also incorporated a genetic risk score for ADHD in the child, mother, and father. Even after these adjustments, each additional month of full breastfeeding up to six months linked to fewer ADHD symptoms at ages three, five, and eight.

To further check for unmeasured family factors, researchers compared siblings across more than 8,200 pairs, including over 5,200 where breastfeeding duration differed. Similar results emerged, supporting the idea that the association is not explained solely by shared family background.

Dr. Yarden Grintal Nes: "It is important to state clearly that a good mother is a good mother, regardless of how her baby is fed. Breastfeeding is not a measure of good parenting but one of many choices, circumstances, and adaptations mothers make for their children."

"These findings strengthen the study's credibility," says Dr. Yarden Grintal Nes, a pediatric specialist at Sheba Medical Center. "The adjustments for genetic background, family traits, and socioeconomic status, along with the sibling comparison, add to the reliability of the results. The research does not prove breastfeeding prevents ADHD, but it supports the possibility of a genuine link rather than research bias."

Researchers suggest several biological mechanisms could explain the connection. Breast milk contains numerous components vital for brain development, including long-chain fatty acids, vitamins, amino acids, oligosaccharides, prebiotics, probiotics, antibodies, immune system elements, and other bioactive substances that may influence nervous system development in early months.

One key hypothesis involves the gut-brain axis. Breast milk contains the amino acid tryptophan, which may affect gut bacteria composition and biological pathways tied to brain development. Prior animal studies cited indicate certain unique sugars in breast milk could enhance attention, working memory, and other cognitive processes.

Beyond nutrition, the act of breastfeeding itself may support development through close mother-infant contact, especially skin-to-skin, which could strengthen bonding and emotional growth with lasting behavioral effects.

Dr. Yarden Grintal Nes notes the proposed mechanisms align with existing scientific knowledge. "Breast milk is not just nutrition but a complex biological system with many components important for brain, immune, and microbiome development," she explains. "This study does not confirm the exact mechanism for the ADHD link, yet it fits accumulating evidence on breastfeeding's benefits for cognitive and neurodevelopmental outcomes alongside other health advantages for baby and mother."

She adds that prior research has connected breastfeeding to fewer developmental delays, reduced neurodevelopmental diagnoses, and better performance on verbal tests and reading-writing assessments.

Although heredity is the main risk factor for ADHD, the disorder is complex and shaped by genetic and environmental influences. It features attention difficulties, hyperactivity, and impulsivity, typically diagnosed in childhood. No cure exists, but symptoms can be managed through behavioral therapy, medication, or both.

The World Health Organization and UNICEF recommend exclusive breastfeeding for the first six months without other foods or drinks, including water. In practice many women cannot meet this goal. The study found average full breastfeeding duration under four months, citing reasons such as medical conditions, work return, and insufficient support. When breastfeeding is not possible, infant formula remains the recommended alternative during the first year.

Dr. Grintal Nes stresses cautious interpretation. "The study does not prove breastfeeding itself prevents ADHD, so there is no basis for concern that not breastfeeding or stopping before six months caused the disorder. Stopping breastfeeding, especially when not by choice, can trigger pain, guilt, or emotional distress. A good mother is a good mother regardless of feeding method. Breastfeeding is not a parenting benchmark but one among many choices mothers make."

Researchers emphasize the observational design means it cannot prove breastfeeding prevents ADHD. The effect size is modest at the individual level yet potentially meaningful at the population level. Findings bolster the notion that breastfeeding may serve as an early protective factor for brain development, though more studies are needed to confirm causality and underlying mechanisms.

"Breast milk is the optimal infant food, with substantial evidence it supports healthy neurological development and provides other significant health benefits," concludes Dr. Grintal Nes. "These new findings reinforce the value of promoting breastfeeding and investing in maternal support systems. Still, ADHD is influenced primarily by genetic factors along with risks such as prematurity, low birth weight, prenatal exposures, and environmental influences."