[Breastfeeding and externalizing behaviors in childhood and adolescence in a birth cohort]

To assess the association between breastfeeding duration and externalizing behaviors in childhood and adolescence.

Data from the 1993 Pelotas Birth Cohort was used. Information on breastfeeding was assessed at 12 months of age. Behavior was assessed at 4 years of age using the Child Behavior Checklist (CBCL), and at ages 11 and 15 years using the Strengths and Difficulties Questionnaire (SDQ), both administered to the mother or caretaker. Of 5 249 cohort participants, those with complete data on breastfeeding and externalizing behaviors were included: 630 children at 4 years of age, 1 277 adolescents at 11 years, and 1 199 at 15 years. Poisson regression with robust variance was used to assess the association between breastfeeding duration and externalizing behaviors.

After adjustment for confounders, children who were breastfed for least 6 months had lower risk of hyperactivity (RR = 0.54; 95%CI: 0.32-0.91) at age 11 compared to those breastfed for less than 1 month. However, no association was observed between breastfeeding duration and externalizing behaviors at ages 4 and 15.

Although breastfeeding for at least 6 months was inversely associated with hyperactivity at 11 years of age no association was observed at 4 and 15 years of age. Further longitudinal studies should focus on other aspects influencing externalizing behaviors, such as presence of the father in the family, domestic violence and abuse, and the quality of mother-child relationship.