Feeding practice during infancy is associated with attention-deficit/hyperactivity disorder and autism spectrum disorder: a population-based study in South Korea.

Attention-deficit hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) are representative neurodevelopmental disorders. Using a nationwide database, we aimed to investigate whether feeding practices in infancy (breastfeeding and the timing of supplementary food introduction) could impact ADHD or ASD development. We evaluated 1,173,448 children aged 4-6 months who were included in the National Screening Program for Infants and Children (NHSPIC) between 2008 and 2014. We observed individuals until 6-7 years of age. Data on feeding type (milk feeding: exclusive breastfeeding [EBF], partial breastfeeding [PBF], exclusive formula feeding [EFF] at 4-6 months of age; supplementary food introduction: < 6 or > 6 months of age) were obtained from the NHSPIC, and diagnoses were based on the International Classification of Diseases, Tenth Revision. In a generalized linear model, children who received EBF had significantly lower incidence of both ADHD (odds ratio [OR]: 0.77, 95% confidence interval [CI]: 0.72-0.82) and ASD (OR: 0.64, 95% CI: 0.60-0.67) than that of children who received EFF. PBF also had a significant protective effect on both ADHD (0.91; 0.85-0.98), and ASD (0.89; 0.83-0.95). The timing of supplementary food introduction was not associated with either ADHD or ASD, although there was an increased risk of ASD in the EFF infants who had supplementary food introduced at > 6 months of age.  Conclusion: Our study strengthens and supports the beneficial effect of breastfeeding on neurodevelopmental disorders in children. Breastfeeding should be encouraged and recommended to promote desirable neurodevelopmental outcomes. What is Known: • Breastfeeding is beneficial for the overall health of children, including neurodevelopmental outcomes and cognitive functions. What is New: • Breastfeeding, especially exclusive breastfeeding, was protective against neurodevelopmental disorders. • The effect of the timing of supplementary food introduction was limited.