Maternal depression and children’s cognitive development : the reasons and conditions of their associations

Context: Cognitive development is an important building block of health and wellbeing because it equips individuals with the necessary skills to increase control over and improve their health as they age. To ensure healthy cognitive development, we need to better understand how the early childhood environment influences development. Maternal depression in early childhood is a prevalent (11-25%) public health problem and a robust risk factor for poor cognitive outcomes in the child. However, there remain important gaps in our understanding of the longitudinal mechanisms through which it influences children’s cognitive outcomes. Understanding why and for whom this association exists can inform the development of interventions to promote healthy child development.  Objectives: The overall aim of this dissertation is to examine mediating and moderating factors of the association between maternal depression and children’s cognitive development using the Developmental Model for Understanding Mechanisms of Transmission as a framework. Specific objectives – each corresponding to a research paper forming the body of this dissertation – are to: (1) summarize existing evidence on mediators of the association between maternal depression and children’s cognitive development; (2) examine the mediating role of children’s school experiences in the association between maternal depression and academic performance, including the moderating role of child’s sex in these associations; (3) examine the role of gene-environment mechanisms in the association between maternal depression and children’s cognitive school readiness; and (4) perform a meta-analysis of the moderating role of child’s sex in the association between maternal depression and cognitive outcomes across childhood and adolescence. Methods: Systematic review and meta-analytic methods were used to address objectives 1 and 4. For objective 2, data from the Québec Longitudinal Study of Child Development were used. Maternal depression was self-reported (between child’s ages 5 months and 5 years); peer victimization and school engagement were parent, teacher, and child-reported (6-10 years); and academic performance was assessed when children were 12 years. Data from the Québec Newborn Twin Study were used for objective 3: self-reported maternal depression (6 and 18 months) and assessment of children’s cognitive school readiness (5 years). Structural equation models, adjusted for confounders where necessary, were used to estimate associations in both cohorts.  Results: The studies in this dissertation show that (1) only a handful of studies have examined mediators of the association between maternal depression and cognitive development, with most identifying maternal cognitions, behaviours, and affect as a mediator; (2) school engagement mediates the association between maternal depression and academic performance in girls only; (3) genetic contributions to children’s cognitive school readiness decrease – while environmental contributions increase – as the level of maternal depression increases; and (4) sex moderates the association between maternal depression and cognitive development, with boys at higher risk of poor cognitive outcomes.  Conclusion: These findings suggest that addressing maternal cognitions, behaviours, and affect can help mitigate the negative effect of maternal depression on children’s cognitive outcomes at the population level. They also suggest that boys are more negatively affected by maternal depression, and that for girls, addressing the impact of maternal depression on their school engagement may lead to improved cognitive outcomes. Further research on additional mediators and moderators can help strengthen our understanding of the association between maternal depression and children’s cognitive development.

Keyphrases: Cognitive development, Maternal depression, Mediators, Moderators, Gene-environment mechanisms, Systematic review, Meta-analysis