Postpartum Depressive Symptoms of Mothers with Reciprocal Social Behavior Problems Linked to Increased Aggression in Infants: Hamamatsu Birth Cohort for Mothers and Children (HBC Study)

Previous studies have led to the assumption that maternal problems in reciprocal social behavior might play an important role in infantile aggression. This study investigated whether maternal problems in reciprocal social behavior were predictive of higher infantile aggression at 18 months of age, and whether maternal postpartum depressive symptoms mediated the association. Participants were 769 mother-child dyads enrolled in the Hamamatsu Birth Cohort for Mothers and Children, in Hamamatsu, Japan. Maternal problems in reciprocal social behavior were evaluated during mid-pregnancy; maternal postpartum depressive symptoms were assessed at 4 weeks after childbirth; and infantile aggression was evaluated at 18 months of age. The results of mediation analysis using structural equation modeling showed that maternal problems in reciprocal social behavior directly increased infantile aggression (estimate = 0.100, 95% CI [0.011, 0.186]), and indirectly increased infantile aggression via maternal postpartum depressive symptoms (estimate = 0.027, 95% CI [0.010, 0.054]), even after controlling for covariates. This is the first study to demonstrate two separate processes in the effects of maternal problems in reciprocal social behavior on early infantile aggression. Corresponding author.