Elizabeth Wall-Wieler, Leslie L. Roos & Ian H. Gotlib

OBJECTIVES: To assess the relation between exposure to maternal depression before age 5 and 5 domains of developmental vulnerability at school entry, overall, and by age at exposure.

METHODS: This cohort study included all children born in Manitoba, Canada, who completed the Early Development Instrument between 2005 and 2016 (N = 52 103). Maternal depression was defined by using physician visits, hospitalizations, and pharmaceutical data; developmental vulnerability was assessed by using the Early Development Instrument. Relative risk of developmental vulnerability was assessed by using log-binomial regression models adjusted for characteristics at birth.

RESULTS: Children exposed to maternal depression before age 5 had a 17% higher risk of having at least 1 developmental vulnerability at school entry than did children not exposed to maternal depression before age 5. Exposure to maternal depression was most strongly associated with difficulties in social competence (adjusted relative risk [aRR] = 1.28; 95% confidence interval [CI]: 1.20–1.38), physical health and well-being (aRR = 1.28; 95% CI: 1.20–1.36), and emotional maturity (aRR = 1.27; 95% CI: 1.18–1.37). For most developmental domains, exposure to maternal depression before age 1 and between ages 4 and 5 had the strongest association with developmental vulnerability.

CONCLUSIONS: Our finding that children exposed to maternal depression are at higher risk for developmental vulnerability at school entry is consistent with previous findings. We extended this literature by documenting that the adverse effects of exposure to maternal depression are specific to particular developmental domains and that these effects vary depending on the age at which the child is exposed to maternal depression.

What’s Known on This Subject:

Exposure to maternal depression is associated with problematic development in offspring, although the specific nature of these difficulties and their association with age at exposure is not well understood.

What This Study Adds:

We documented specificity in the effects of children’s exposure to maternal depression in early childhood, with the strongest effects on social competence and emotional maturity and among children who were exposed to maternal depression shortly before starting school.

Early childhood development is affected by a wide range of genetic, biological, social, and psychological factors.1,2 Maternal mental health has been identified as a particularly important factor affecting childhood development, influencing children’s growth, cognitive development, and psychosocial well-being.3 In this context, the most common maternal mental health condition is depression, affecting ∼1 in 7 women overall and 1 in 8 women during the postpartum period.4–7 Researchers have found that children whose mothers have high levels of depressive symptoms are characterized by significantly poorer cognitive development than children whose mothers have few or no depressive symptoms.8,9 However, most researchers studying the relation between maternal depression and early childhood development have used survey results from a small number of mother-child pairs and/or have examined development using composite scores such as the Bayley Scales of Infant Development.8,10 Moreover, researchers have measured child development at different ages (from a few months to 5 years), both within and across studies, and have rarely examined children’s age at exposure to maternal depression as a factor affecting their development.8

To address these limitations, we linked several population-based clinical and social databases from Manitoba, Canada. Specifically, we assessed the relation between maternal depression and children’s developmental vulnerability at school entry and assessed whether discrete areas of development are affected differentially by exposure to maternal depression before age 5 years. In addition, we examined whether the relation between exposure to maternal depression and developmental vulnerability at school entry varies on the basis of the age at which children are exposed to their mother’s depression.

Of the 52 103 children in our cohort, 9938 (19.1%) had a mother who was diagnosed with depression between their birth and fifth birthday. Compared with mothers without a diagnosis of depression, mothers diagnosed with depression before their child’s fifth birthday were more likely to be <25 years of age when they had their first child, to live in social isolation, to be unmarried, and to live in a low-income neighborhood at the birth of their child; they were also more likely to have smoked or used drugs or alcohol during pregnancy (Table 1). Children whose mothers had a diagnosis of depression before they turned 5 were more likely to have been born preterm. All of these variables were included as covariates in the primary analyses.

Early Childhood Maternal Depression

Children whose mother had a diagnosis of depression before they reached age 5 years had a 1.17 (95% confidence interval [CI]: 1.11–1.23) times increased risk of having a developmental vulnerability at school entry (Table 2). Developmental domains associated most strongly with maternal depression during early childhood were social competence (aRR = 1.28; 95% CI: 1.20–1.38), physical health and well-being (aRR = 1.28; 95% CI: 1.20–1.36), and emotional maturity (aRR = 1.27; 95% CI: 1.18–1.36).

Children of Sisters Discordant for Depression

In 836 families, 1 mother had a diagnosis of depression in the 5 years after the birth of her child, but her sister did not. In this comparison, children of mothers with depression showed lower levels of social competence (aRR = 1.74; 95% CI: 1.26–2.38) and emotional maturity (aRR = 1.48; 95% CI: 1.09–2.01) (Table 3); the domain of physical health and well-being, which was found (as mentioned previously) to be related to exposure to maternal depression, did not distinguish children of sisters who were discordant for depression.

Age at Exposure to Maternal Depression

The number of children exposed to maternal depression increased from 3656 (7.0%) who were exposed between birth and their first birthday to 4738 (9.1%) who were exposed between their fourth and fifth birthday. For the 3 domains in which maternal depression was related to children’s developmental vulnerability (physical health and well-being, social competence, and emotional maturity), the greatest risk of vulnerability was among children exposed to maternal depression between their fourth and fifth birthday (Fig 2). Unadjusted relative risk and aRR of developmental vulnerability by age at exposure are presented in Supplemental Table 4.

Discussion

In this population-based cohort study, we found that children exposed to maternal depression in early childhood were at greater risk of experiencing developmental vulnerability at school entry than children not exposed to maternal depression. Importantly, exposure to maternal depression in early childhood was associated with specific forms of developmental vulnerability. Findings both from the full cohort and from a family-based subcohort revealed that early childhood exposure to maternal depression was associated most strongly with vulnerabilities related to social competence and emotional maturity. In addition, exposure to maternal depression had the strongest effects on developmental vulnerability when children were exposed shortly before school entry.

Researchers have documented consistent associations between depression and difficulties in both social functioning and emotion regulation.24–27 The finding in this study that children’s exposure to maternal depression is associated with problematic functioning in these 2 domains at as early as 5 years of age extends the literature and offers insight into the origins of these psychosocial difficulties. It is noteworthy that these difficulties were reported by the children’s teachers, avoiding negative biases inherent in having mothers with depression serve as informants.28 It is also important to note that children’s difficulties in these 2 domains were evident even when comparing with offspring of sisters discordant for depression, suggesting that this problematic functioning in young children exposed to maternal depression is not due solely to genetic factors.

We found little to no relation between exposure to maternal depression and language and cognitive development in children at school entry. Previous studies have revealed that children who were exposed to maternal postpartum depression were slightly more likely to fail object concept tasks at 18 months (differences that were stronger in male than in female toddlers).29 Importantly, alterations in cognitive development that may be a function of maternal depression seem to diminish over time. Consistent with our findings, researchers have reported that by age 5 years, children’s performance on cognitive tasks were not associated with the mother’s depression.30,31 Instead, poorer cognitive function was associated with early experiences of insensitive maternal interaction, stimulation at home, and social class.31

The findings reported in this article need to be extended in future research. In particular, investigators should work to elucidate the mechanisms that underlie this intergenerational transmission to young children of mothers with depression at risk for social and emotional difficulties, focusing on aspects of the caregiving environments and behaviors to which these children are exposed. Investigators of these studies should also attend to protective factors that may confer resilience to children exposed to maternal depression.32 Such research will have significant implications for prevention of what is likely to be a lifelong cascade of problematic psychosocial functioning in offspring of mothers with depression.2

This study has limitations that typify observational studies in general. First, we were limited to information that could be obtained from existing data files, requiring us to use proxies for some of our measures. For example, maternal depression was defined on the basis of recorded diagnoses and prescriptions. Importantly, because claims data are used to measure treatment for a condition, not the presence of a condition, the true prevalence of depression in the community is underestimated,33 although we should note that this was not a study of the prevalence of maternal depression. Second, we do not know when the first onset of maternal depression occurred, only when the mother sought treatment of her depression, nor can we determine the severity of depression. Third, we are limited in the possible confounding variables for which we can adjust. For example, parenting style has been found to be related to early childhood development,34 but we do not have data on parenting style. In this context, however, parenting style can be influenced intergenerationally, and sisters have been found to have similar parenting styles35; importantly, we were able to account for this, in part, in our discordant cousins analysis. Finally, we lack information on fathers. Although mothers tend to be the primary caregiver, researchers have found that exposure to maternal depression has stronger effects on child development in the presence of fathers who also have a psychiatric condition.36

This study revealed that children exposed to maternal depression (particularly if the exposure was before age 1 or shortly before school entry) were at higher risk of developmental vulnerability at school entry. Although children exposed to maternal depression were at increased risk of developmental vulnerability at school entry, ∼70% of children exposed were not identified as vulnerable on any of the 5 developmental domains. To improve the outcomes of children exposed to maternal depression, future research should be focused on these children and what made them resilient to identify factors that could prevent young children of mothers with depression from experiencing developmental vulnerabilities.32 In addition, the relations we observed between maternal depression and child development could be affected by other family-level factors, such as the presence and characteristics of siblings. In future research, investigators should examine whether and how having an older or younger sibling (and whether these siblings have developmental or mental health conditions) affects the relation between maternal depression and developmental difficulties in their offspring.