When Berit Skretting Solberg began examining data from nearly 40,000 Norwegian families, she wasn't sure what she would find. What she discovered was striking: children who were exclusively breastfed for up to six months showed measurably fewer ADHD symptoms at ages 3, 5, and 8 compared to those who received less breast milk. The association held true for both boys and girls, and proved strongest at the younger ages tested.
The study, published in Biological Psychiatry and conducted by researchers at the University of Bergen, drew from the Norwegian Mother, Father and Child Cohort Study, one of the world's largest health studies of mothers and children. Solberg, a psychiatrist and researcher at the Department of Biomedicine, worked with co-authors to analyze breastfeeding patterns reported by mothers when their children were six months old, then tracked those children for years afterward.
Breast milk contains a remarkable array of components that support infant development — long-chain fatty acids critical for brain growth, antibodies that strengthen the immune system, beneficial bacteria that colonize the gut, and amino acids that serve as building blocks for the nervous system. "It is well established that psychiatric symptoms and disorders can be influenced by both genetic and environmental factors," Solberg noted.
The researchers were careful to account for the fact that mothers with ADHD symptoms tend to breastfeed less frequently and that children who are later diagnosed with ADHD can be more challenging to nurse. After adjusting for genetic risk factors and socioeconomic differences — and even comparing siblings within the same families who received different amounts of breast milk — a protective effect remained. "Even after these adjustments, there was a clear but moderate protective effect of the duration of exclusive breastfeeding on later ADHD symptoms," Solberg said.
The findings offer a hopeful note: while genetics remain the strongest known risk factor for ADHD, this research suggests that environmental factors like breastfeeding may help shape a child's neurological development in protective ways. Solberg cautions that observational studies cannot prove direct causation, and the MoBa cohort tends to include more educated families who breastfeed longer than the general population — meaning the protective effect could potentially be even larger in other groups.
What the study does suggest, however, is that the simple act of breastfeeding — already known to boost immune function and create bonding benefits — may carry unexpected advantages for developing brains. "Since ADHD, like other neurodevelopmental disorders, is influenced by multiple factors, our study suggests that the extent of breastfeeding may also help protect against the development of ADHD symptoms in young children," Solberg said.