Maternal postpartum depressive symptoms and infant externalizing and internalizing behaviors

• Significant associations between PPD symptoms and infant behavior in initial models.
• No association between PPD symptoms and infant behaviors in adjusted models.
• Combined effect of confounding factors seems to explain the findings of no association.

Maternal postpartum depression has been shown to be one of the main predictors of externalizing and internalizing behaviors in toddlers and adolescents. Research suggests that presence of such behaviors can be observed as early as infancy. The current study uses longitudinal data from 247 mothers to examine the relationship between postpartum depressive symptoms at 8 weeks and the infant's externalizing and internalizing behaviors at 12 months. In unadjusted linear regression models, there were associations between postpartum depressive symptoms and infant externalizing behaviors (β = 0.082, SE = 0.032, p = 0.012) and internalizing behaviors (β = 0.111, SE = 0.037, p = 0.003). After controlling for potential confounding factors, including maternal age, race, education, home ownership, smoking status in the postpartum period, marital status, parenting stress, and happiness from becoming a parent, the associations between postpartum depressive symptoms and infant externalizing (β = 0.051, SE = 0.034, p = 0.138) and internalizing behaviors (β = 0.077, SE = 0.040, p = 0.057) were reduced and became non-significant. Furthermore, in these models the total amount of variance explained was 17.2% (p < 0.0001) for externalizing behaviors and 10.5% (p < 0.01) for internalizing behaviors; the only significant predictor of externalizing behaviors was maternal age (β = −0.074, SE = 0.030, p = 0.014), and of internalizing behaviors was white non-Hispanic ethnicity (β = −1.33, SE = 0.378, p = 0.0005). A combined effect of the confounding factors seems to explain the finding of no significant independent association between postpartum depressive symptoms and infant externalizing and internalizing behaviors.