The research of Lynne Murray and Peter Cooper in the 1990s was pivotal in terms of demonstrating the negative effects of postpartum depression on the cognitive development of young children and played an important role in drawing attention to the often overlooked but prevalent problem of postpartum depression. While some studies have documented that, in many cases, these cognitive deficits do not persist over time, others have demonstrated more persistent effects of postpartum depression on cognitive development and behavior.
Most of these early studies were relatively small and assessed younger children, usually before the age of 5 years. What is more sparse is information on the long-term effects of postpartum depression on children’s cognitive development. One measure of long-term cognitive outcomes is intelligence quotient or IQ; however, studies looking at postpartum depression and children’s IQ have yielded inconsistent findings.
In order to better understand the association between maternal postpartum depression and offspring IQ, researchers recently conducted a meta-analysis, collecting articles examining the IQ of offspring two years and older in women with and without postpartum depression. Nine studies were identified. Using the Newcastle-Ottawa Scale, 7 of the 9 studies were considered to be of high quality and were used for the analysis.
The final analysis included data from 974 children. The children born to mothers with postpartum depression had lower verbal and full IQ scores than the children of nondepressed mothers. For full IQ, the pooled weighted mean difference between the children of depressed mothers and non-depressed mothers was -4.086 (95% CI, -6.578 to -1.594). For verbal IQ, the pooled standard mean difference between the children of depressed mothers and non-depressed mothers was smaller, -0.361 (95% CI, -0.564 to -0.158). Age at evaluation and socioeconomic status did not affect the results of the analyses.
These findings suggest that postpartum depression may have a negative effect on children’s cognitive development, as measured by IQ. The authors of this study go on to speculate on how postpartum depression affects cognitive development. They note that the infants of nondepressed mothers are more likely to exhibit left frontal electrical activity, whereas the infants of depressed mothers exhibit right frontal electrical activity. This pattern indicates that the infants of depressed mothers are more likely to be distressed, which may have a negative effect on the infant’s ability to handle novel stimuli and may adversely affect learning. In addition, they note that postpartum depression may affect the mother’s behavior. With maternal depression, there is often a lack of synchrony between an infant’s behaviors and the mother’s responses, which may have a negative effect on subsequent learning abilities.
Given these findings, a better understanding of how maternal depression affects children’s cognitive development is essential as it may help us to target interventions which minimize the negative effects of maternal depression on the child.