Maternal postnatal depression and children's growth and behaviour during the early years of life: exploring the interaction between physical and mental health.

OBJECTIVE: To assess the association between maternal postnatal depression and child behaviour problems and child growth at age 2 years. METHODS: This was a longitudinal birth cohort study in Johannesburg, South Africa. Primary analysis on the 'Birth to Twenty' cohort was performed for the association between maternal postnatal depression and child behaviour problems (n=1035) and growth (n=891) at age 2 and subgroup analyses (n=635) were carried out to assess the role of poor child growth in this association. Main outcome measures were the association between maternal postpartum depression (measured at 6 months postnatally using the Pitt depression inventory) and child behaviour problems (Richman child behaviour scale) and child growth at age 2 years. RESULTS: Maternal postnatal depression was significantly associated with child behaviour problems at age 2, independent of socioeconomic status (beta=0.353, p value=0.015). There was some evidence that children of depressed mothers were also at increased risk for having stunted growth, compared to non-depressed mothers (OR 1.61 (95% CI 1.02 to 2.56). The association between postnatal depression and child behavioural problems was significantly mediated by the stunted growth of the child (beta=0.294, p value=0.111). CONCLUSIONS: Maternal postnatal depression is associated with later child behaviour problems independent of the socioeconomic status of the family. This association is mediated by the child's growth, demonstrating the importance of considering a child's physical and mental health together.