Examining the relationship between infant feeding practices and child hyperactive/inattentive behaviours in a Canadian sample
Attention deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder diagnosed in childhood. It is largely accepted that ADHD is a product of gene-environment interactions and method of infant feeding has been proposed as a factor influencing the expression and/or severity of ADHD. The objectives of this study were to determine the relationship between infant feeding (i.e. formula feeding or breast feeding) and subsequent hyperactive/inattentive (H/I) behaviours and ADHD diagnosis and if the relationship between infant feeding and academic performance is moderated by H/I scale score. This study used data from the 2000/1, 2002/3, 2006/7 and 2008/9 cycles of the National Longitudinal Survey of Children and Youth (NLSCY) (n= 3,895) to follow children longitudinally from the age of 0 to 1 years old to 6 to 7 years old. Infant feeding at 0 to 1 years old, and child H/I score, ADHD diagnosis and academic performance scores at 6 to 7 years old were reported by the biological mother. Multivariable logistic and linear regression were used to determine the relationship between infant feeding and H/I score, ADHD and academic performance adjusting for a range of sociodemographic, birth and home environment factors. Breastfeeding for more than 12 months was found to be significantly associated with decreased H/I scale scores in the most adjusted model (OR=0.3; 95% CI 0.2-0.8, p<0.01). Infant feeding was not associated with ADHD diagnosis and there was no moderating effect of the H/I score on the relationship between breastfeeding and academic performance. A small proportion of mothers breastfeed beyond one year in Canada and this study shows that there might be important child benefits incurred by breastfeeding for longer than 12 months.