NORWAY — Children who were fully breastfed for longer durations showed modestly fewer symptoms of Attention-Deficit/Hyperactivity Disorder (ADHD) between the ages of 3 and 8, according to a study published in Biological Psychiatry. Researchers accounted for genetic and family-related factors in the analysis of ADHD symptoms.

The study utilized data from the Norwegian Mother, Father and Child Cohort Study (MoBa) and the Medical Birth Registry of Norway (MBRN). Researchers followed a birth cohort that included 37,643 children and 18,349 complete family units. Mothers completed standardized questionnaires to calculate ADHD scores for each child at ages 3, 5, and 8, while information on breastfeeding was self-reported by mothers at six months.

For each month of full breastfeeding, ADHD scores in the child were 0.06 to 0.08 lower at all ages measured in the study. Full breastfeeding was defined as either exclusive or predominant breastfeeding, with less than weekly use of water-based drinks or fruit juices in the latter case. Infants who were fully breastfed for six months served as the reference group in the category-wise analysis.

Shorter durations of full breastfeeding were associated with higher ADHD symptom scores at ages 3, 5, and 8 when compared to the reference group. The difference in ADHD scores for shorter breastfeeding durations ranged from 0.33 to 0.55 higher at age 3 and from 0.21 to 0.46 higher at age 8. The greatest increase in ADHD scores was observed in infants who received only partial breastfeeding for less than four months.

Sibling-pair analyses, which involved siblings with different breastfeeding exposures, yielded results similar to the main findings. The statistical model explained approximately 4% to 7% of the total variance in ADHD symptoms. However, results for the no-breastfeeding group were inconsistent across the three ages measured, and associations between breastfeeding and ADHD symptoms were weaker when the data were stratified by sex. ADHD is characterized by persistent inattention, hyperactivity, and impulsivity; an estimated 70% to 80% of ADHD heritability is attributed to genetics.