Association between maternal employment and the child's mental health: a systematic review with meta-analysis

Introduction

Mental health disorders often already appear during childhood and adolescence. Meta-analytic data provide a global prevalence rate of 13.4% in children up to age 18 years [1] with inclusion of subclinical problems leading to even higher rates [2]. Mental health problems can already be noticed in early childhood [3-5] thereby often operationalized as behavior problems (BP). Once evolved, mental health problems are highly stable and often persist into adulthood [6] thereby being associated with adverse life outcomes, e.g., reduced long-term (mental) health [7, 8], suicidality [8], and delinquency [9]. As effective prevention and intervention strategies are highly warranted research has focused on variables associated with early mental health problems. Such factors are located in the child itself, e.g., its gender [10, 11] and temperament [12], as well as in children’s environment. Examples include family structure [13], parental mental health [10, 11, 13], and socio-economic status [11, 14]. Due to a substantial rise in maternal workforce participation in recent decades [e.g., 15] research also focused on the role of maternal employment.

Linking maternal employment and child mental health theoretically

Several disciplines address a potential association of maternal employment and child mental health, i.e., developmental psychology, sociology, and economics [16, 17]. The household economics framework for instance claims that families tend to maximize their well-being based on two resources, i.e., time and money. Parents face the decision whether well-being is maximized by maternal employment leading to increased financial resources that can be used to purchase goods and services, e.g., child care, or is promoted by mothers staying at home to spend more time with their children, providing attention and emotional support. Maternal employment could lead to poorer child mental health in case goods and services purchased do not compensate well enough for lost parental care [see 18].

In light of role strain theories, the intervening role of maternal health seems of importance. The scarcity hypothesis assumes that as time and energy are limited one could not have enough energy for every role to be fulfilled, e.g., the role as a mother and the role as an employee, thus creating overload and stress resulting in poorer health [19]. As evidence clearly indicates the positive link between the mental health of mothers and their children [e.g., 20] maternal employment should be associated with poorer child mental health. However, the exact opposite would be assumed following the enhancement hypothesis that denies a fixed amount of time and energy and presumes that every new role adds sources of self-esteem and social support leading to better health [21, 22].

Hence, when investigating the association of maternal employment and child mental health one could rely on various theories stemming from different disciplines [for a broader overview please refer to 17, 23], which clearly hampers the formation of distinct hypotheses on the variables’ of interest association. Positive and negative associations could even offset each other resulting in a missing link [16]. Furthermore, special emphasis has to be given to sample characteristics as maternal employment could be differently associated with mental health among various subgroups of children. Here, children’s age constitutes an important factor as especially early maternal return to work has been extensively researched and discussed controversially, e.g., based on concepts of attachment and critical periods in children’s lives [see 23].

Previous research on the association of maternal employment and child mental health

Indeed, the extensive body of research on the association of maternal employment and child mental health so far has produced mixed findings leading to different conclusions [see 18, 23]. In recent years, various reviews emphasized that such an association, if any, may arise when early maternal employment is investigated underlining the need to consider children’s age. Especially employment within the first year postpartum has been shown to be adversely related to child mental health in terms of BP [24-26] whereas later employment could even be beneficial [24]. Concerning intensity, working very long hours was seen as potential issue [24]. Further variables important to consider are, among others, ethnicity [25] due to possible differences in, e.g., normativity of maternal employment and the home environment [see 16], maternal preferences [24], and working conditions [24], including working schedules [27], and income [24, 25].

A meta-analysis also focusing on early maternal employment, i.e., during child age 0–3 years, found somewhat different associations with BP. Here, children of employed mothers showed less internalizing behavior problems (IBP) than children of unemployed mothers. This finding extended to overall and externalizing behavior problems (EBP) in samples predominantly consisting of one-parent families, thereby underlining the importance of family structure. Despite that, in terms of working intensity children of mothers working full-time exhibited more BP and EBP than children of unemployed mothers [23].

Due to their meta-analytic procedure, results of Lucas-Thompson and colleagues [23] have to be considered most trustworthy. However, when trying to explain the mixed findings some limitations of previous research need to be considered. First, authors focused on overall measures of mental health, i.e., BP, EBP, and IBP, thereby relying on various operationalizations and methods of measurement. However, maternal employment could be differently associated with single subordinate measures such as aggressiveness or hyperactivity. Second, despite the focus on early maternal employment results were aggregated over a wide range of children’s age, i.e., including studies that measured mental health at some time during infancy, childhood, or adolescence. However, maternal employment may be differently linked to child mental health depending on child age at time of both variables’ measurement. As younger children cannot take care of their own having a working mother may have stronger implications in infancy and early childhood. Third, included studies predominantly stemmed from the US, e.g., using data of the National Longitudinal Survey of Youth (NLSY79) that investigates children born by the end of the last century. In recent years, more investigations focusing on children born considerably later added to the literature, e.g., the Early Childhood Longitudinal Study – Birth Cohort (ECLS-B). As maternal workforce participation has risen in recent decades [e.g., 15] and therefore has become more normative, we may find different implications of maternal employment for children depending on their year of birth. Finally, maternal employment covers more than employment status per se or working amount (including comparisons of full-time and part-time employment). When further focusing on other employment characteristics, e.g., duration or timing of return to work, more distinctive conclusions could emerge.

Hence, missing associations of maternal employment and child mental health could be a result of aggregating different health measures either positively or negatively linked to the former or mixing results obtained by investigating different age groups. Associations found could be biased by the same mechanisms as well. Moreover, it remains unclear whether results can be generalized to very recent findings on the association of maternal employment and child mental health including data generated by newer cohort studies. Beside concentration on maternal employment status other employment characteristics may be important as well.

Objectives and research questions

This systematic review with meta-analysis covers evidence on the association of maternal employment and child mental health from years 2005 to 2020 to update findings and overcome shortcomings of previous research. In light of potential offsetting effects, separate analyses will be run for every single indicator of child mental health found, if possible. Studies to be included have to investigate children of a specific age group, i.e., 0–7 years, to prevent from mixing results on children and adolescents. We will not only focus on maternal employment status and working amount but also summarize results on employment duration and timing. By doing so, the following research questions will be addressed:

Is maternal employment associated with the mental health of children 0–7 years of age?
Which factors constitute important moderators of the association of interest?

Methods

A comprehensive literature search was conducted to identify and summarize the results of recent observational studies examining the association of maternal employment and child mental health. The review’s study protocol has been preregistered (PROSPERO) and is available online.

Initially, three different databases (PsycINFO, PubMed, and Web of Science Core Collection) were searched for relevant literature from 2005 to 12 June 2018. The year 2005 was considered as starting point to include recent evidence only [for an analysis of research from 1960 to 2010 please refer to 23]. In October 2021 a search update was conducted to cover evidence published until 11 March 2020, when the outbreak of COVID-19 was declared a pandemic [28]. As the pandemic impacts both maternal employment, e.g., by schools having been closed [29], and child mental health [e.g., 30] bias in the variables’ association could emerge we wanted to prevent from. Because of technical issues searching PsycINFO yielded results listed until 31 March 2020. A comprehensive search string was used consisting of keywords describing the population, treatment and comparison conditions, and the outcomes of interest (for more details please refer to the Online Resource and see Supplementary Box S1). Additionally, reference lists of included studies, the previously published meta-analysis [23], and former reviews [24, 27, 31] were manually screened for further relevant literature. Dissertations and working papers were considered, if available, to cover grey literature.

Eligibility criteria

Inclusion and exclusion criteria were determined by the review’s PICOS-scheme. To be eligible for the qualitative synthesis the studies´ population (P) had to consist of children 0–7 years of age. Studies were excluded if the sample (also) comprised children eight years or older.

In terms of the intervention (I), studies were included if children of working mothers were compared to children of non-working mothers (comparison C). Alternatively, the comparison could be drawn between children of mothers working more hours (e.g., employed full-time), longer (in terms of employment duration), or earlier after birth and children of mothers working less hours (e.g., employed part-time), shorter, or later after birth. In either case, maternal employment had to refer to child age 0–7 years and constitute the independent variable. Studies investigating family employment, e.g., by inclusion of grandmothers, were excluded if they did not report findings for maternal employment separately. In case an appropriate control group was missing or maternal employment did constitute the dependent variable studies were excluded as well.

In terms of the outcome (O), child mental health could be operationalized by BP, e.g., EBP or IBP, single subordinate measures, e.g., aggression or anxiety, and diagnosed mental health disorders, e.g., Attention-Deficit/Hyperactivity Disorder, as the focus is on both mental health problems and disorders. Prosocial behavior (PB) constituted an additional but positive outcome. The (non-) significance of the investigated association with maternal employment had to be clearly stated, i.e., in text form or by provided figures. Studies were excluded if the studies’ outcome referred to other areas than mental health, e.g., somatic conditions, cognitive development, or skill formation. Self-esteem and temperament were not considered eligible outcomes either.

Concerning the included studies’ design (S), only observational investigations published in English or German language were considered eligible. Intervention studies, reviews or meta-analyses, case reports, case series studies, commentaries, editorials, and expert opinions were excluded. To be eligible for the quantitative synthesis, studies had to additionally report a measure of effect size or present information allowing for calculation of a corresponding measure.

Study selection

Eligibility of studies was examined by screening based on title/abstract first. Afterwards full-texts were retrieved and assessed for inclusion. In both cases, this was done by two reviewers (M.K., M.L.) independently. If consensus could not be reached a third reviewer (S.G.-N.) was consulted; majority won.

Data extraction and coding of study variables

Data were extracted by two reviewers (M.K., M.L.) using a standardized extraction form [32] modified based on the review’s PICOS-scheme. Maternal employment was represented in form of a categorical variable in case studies provided employment status, e.g., by comparing children of employed and unemployed mothers or by differentiating among children of full-time and part-time employed mothers, or in case results on timing of return to work were presented. In contrast, maternal employment constituted a continuous variable if studies provided information on working amount in form of a working hours measure or information on employment duration. With BP, EBP, IBP, and PB four categories of child mental health outcomes were considered. BP referred to measures of behavior in general, e.g., measured by use of the total score of the Strengths and Difficulties Questionnaire [SDQ; 33]. EBP were assessed, e.g., by subscales of the Child Behavior Checklist [e.g., 34] and included aggression, hyperactivity/inattention, conduct problems, and disruptive behavior. IBP were assessed, e.g., by subscales of the SDQ and referred to emotional problems, anxious/depressed behavior, and withdrawn behavior/peer problems. PB was assessed, e.g., by the corresponding subscale of the SDQ and covered positive and cooperative behavior as well.

Potential moderators included study characteristics, i.e., data source (cohort study or country data stemmed from), design (cross-sectional, longitudinal), and adjustment of values provided (no, yes) supplemented by studies’ methodological quality (low, moderate, or high risk of bias) as assessed by two reviewers (M.K., M.L.) using an adapted risk of bias procedure based on Ijaz and colleagues [35]. Some aspects of the initial checklist were omitted as they were not considered relevant for our systematic review with meta-analysis, e.g., blinding (not feasible in observational studies) and reporting of hypotheses tested (association of maternal employment and child behavior did not constitute the research focus of every included study). The resulting checklist consists of five major domains essential for study quality, e.g., recruitment procedure and measurement of maternal employment and child behavior, and three minor domains, e.g., chronology and funding. For nearly every domain risk of bias was considered low, high, or unclear. Study-level risk of bias was then rated as low (i.e., low risk in every major domain and at least two minor domains), moderate (i.e., low risk in at least four major domains and one minor domain), or high (i.e., low risk in less than four major domains or no minor domain). If consensus could not be reached a third reviewer (S.G.-N.) was consulted; majority won.

Sample characteristics considered as potential moderators included child age at outcome assessment (in years, if an age range was given the mean was used for analyses), child gender (girls vs. boys vs. mixed), and timing of maternal employment (in years, if a range was given the mean was used for analyses). Ethnicity of mother and/or child was coded as majority White vs. majority Black vs. majority Hispanic (with majority referring to at least 75% of the sample) vs. mixed vs. not reported. Categorization of maternal marital status included majority coupled mothers vs. majority lone mothers (with majority again referring to at least 75% of the sample) vs. mixed vs. not reported.

Synthesis of results and meta-analytic procedures

First, qualitative syntheses of evidence for the various outcomes under investigation were conducted. If both unadjusted and adjusted analyses were carried out, only results of the adjusted analyses were considered. In case of various adjusted analyses, we focused on results of the respective fully-adjusted models.

Quantitative syntheses of evidence followed in case at least two studies either directly provided corresponding, comparable effect sizes or data allowing for their calculation. The effect size used depended on the intervention’s measurement level. For categorical employment indices the Odds Ratio (OR) was calculated. Maternal unemployment or part-time employment constituted the respective reference categories. In case of continuous employment indices, the correlation coefficient r was calculated. A positively signed value indicated that working more or longer was associated with a higher level of the respective outcome. Note that interpretation therefore differs for negatively labelled outcomes, e.g., BP (higher score is adverse), and positively labelled outcomes, e.g., PB (higher score is good). In case OR or r, respectively, were not provided directly they were calculated based on other statistics given. To include results based on β we followed the approach of Peterson and Brown [36]. In general, adjusted results were preferred. However, if adjusted values did not allow for effect size calculation unadjusted values were used. Effect sizes were generated with the study as the unit of analysis. If a study provided data on independent subgroups, e.g., girls and boys, or various comparisons, e.g., employed full-time vs. not employed and employed part-time vs. not employed, the mean of these effects was used to form a single effect size, e.g., employed vs. not employed. In case a single study yielded multiple effects based on the same sample, e.g., when measuring the respective outcome twice a combined effect size was used to prevent from violation of the assumption of independence. Summary effects were then computed by means of a random-effects model. For meta-analyses including five or less studies results based on the fixed-effects model were considered, too as estimation of between-study variance is less precise when the calculation of a summary effect is based on such a small number of studies [37]. Homogeneity was evaluated using the Q statistic. If homogeneity could not be assumed moderator analyses followed. Unadjusted effects of each potential moderator variable were assessed and supplemented by analyses examining the joint contribution of important moderators, if possible. Level of significance was set at p < .05. Again, studies served as units of analysis. Only in case a single study yielded multiple effects based on independent subgroups of sample-level moderators these subgroups served as units of analysis. If multiple effects of single studies still had to be combined (see above) covering different manifestations of study- or sample-level moderators we handled this dependent on the moderator under investigation. For design a third category (mixed) was introduced. Child age and timing of maternal employment were either set to the value most of the effects were based on or to their respective mean when majority was missing.

All analyses were carried out with Comprehensive Meta-Analysis [38]. For moderator analyses the metaregression tool was used.

Results

With duplicates removed, the search process yielded 5,381 results screened for eligibility based on title and abstract first. Afterwards 297 full-texts were retrieved. Figure 1 depicts the whole process in more detail. In total, 41 studies were considered in the qualitative syntheses; 27 studies were included in the quantitative syntheses. Please refer to the Online Resource for a corresponding reference list.

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Table 1 provides brief information on study- and sample-level characteristics, for more details please refer to the Online Resource (Supplementary Tables S1, S2, and S3; extensive information on results of included studies appear in Supplementary Tables S4, S5, S6, and S7). In total, 34 studies focused on maternal employment status or working amount, whereas eight studies investigated employment duration, and six studies included analyses on timing of return to work. Child mental health was operationalized by BP in 15 studies, by EBP in 26 studies, by IBP in 15 studies, and by PB in nine studies. Analytical sample sizes varied from n = 49 to n ≈ 10,100. In 20 studies the association of interest was investigated longitudinally and nearly every study provided adjusted results. Most research stemmed from the US and relied on data of large cohort studies. Unfortunately, risk of bias had to be considered high for a huge majority (see Supplementary Table S3). Turning to sample characteristics, children were ten months [39] to 7.5 years old [40, 41] at outcome assessment. Studies investigated the association in both genders, with only few of them providing distinct estimates for girls and boys. Timing of maternal employment varied from the first year [e.g., 42] to seven years postpartum [43]. Most studies focused on samples of mixed ethnicity investigating (majority) coupled mothers.

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Overall behavior problems

Comparing children of employed and unemployed mothers, four out of 10 studies [39, 44-52] pointed to employment being associated with less BP [44, 45, 48]. Subgroup analyses of Berger and colleagues [47] emphasised the importance of ethnicity. In Hispanic children maternal employment was linked to higher levels of BP whereas in Black children it was associated with lower levels of BP.

A meta-analysis including eight studies [44, 45, 47-52] indicated no association of maternal employment status and BP based on the random-effects model (OR = 0.717 [0.472 – 1.088], P = .118). As the hypothesis of homogeneity had to be rejected (Q (7) = 151.904, P < .001) moderator analyses followed (see Online Resource, Supplementary Table S8). At study-level, data source (Q (5) = 22.01, P < .001) was of importance. When compared to ECLS-B results MCS data were associated with a lower effect size (b = -1.104, P < .001). Here, being employed was linked to lower BP. When taking data source as dummy for country British data still were associated with a lower effect size (b = -0.821, P < .05). Focusing on sample characteristics, ethnicity emerged as moderator (Q (3) = 16.970, P < .001). In comparison to (majority) White samples both samples of mixed ethnicity (b = 0.924, P < .001) and samples without information on ethnicity (b = 0.786, P < .01) were associated with a higher effect size. Here, being employed was linked to more BP. Due to the small number of studies, joint effects of data source and ethnicity could not be assessed.

Focusing on full-time vs. part-time employment, results of six available studies [44, 49, 50, 53-55] did not yield any associations with BP. In a meta-analysis including four studies [44, 49, 50, 54] no summary effect emerged, neither based on the random-effects model (OR = 0.996 [0.761 – 1.304], P = .976) nor the fixed-effects model (OR = 1.020 [0.941 – 1.106], P = .631). As the hypothesis of homogeneity had to be rejected (Q (1) = 22.918, P < .001) moderator analyses followed (see Supplementary Table S8). At study-level, adjustment (Q (1) = 6.30, P < .05) was of importance with adjusted results being associated with a higher effect size (b = 0.454, P < .05). Here, full-time employment was linked to more BP. Focusing on sample characteristics, timing of maternal employment emerged as moderator (Q (1) = 6.30, p < .05). Measuring maternal employment later in children’s life was associated with a higher effect size (b = 0.121, P < .05). Here, full-time employment was linked to more BP. In an adjusted analysis including both characteristics, i.e., adjustment and timing of maternal employment, none of the single coefficients remained significant.

Further four studies [40, 41, 44, 48] focused on employment duration. In analyses of Kiernan and Mensah [48] and McMunn and colleagues [44], both using MCS data, single results indicated longer employment being linked to lower BP. A meta-analysis including two studies [41, 44] indeed indicated an association of maternal employment duration and BP based on both the random-effects model (r = -.072 [-.123 – -.020], P < .01) and the fixed-effects model (r = -.082 [-.109 – -.055], P < .001). Longer employment was associated with less BP (see Figure 2). As the hypothesis of homogeneity could not be rejected (Q (1) = 2.168, P = .141), no moderator analyses followed.

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Only a single study [50] included analyses on timing of return to work. Here, no interpretable results emerged.

Externalizing behavior problems

Overall externalizing behavior problems. Comparing children of employed and unemployed mothers, five out of 11 studies [6, 16, 49, 56-63] yielded significant but mixed results. Employment was linked to either less EBP [6, 61] or more EBP [6, 58, 59, 63], the latter especially in cases of full-time employment [58, 59]. A meta-analysis including seven studies [6, 16, 49, 58-61] indicated no association of maternal employment and EBP based on the random-effects model (OR = 1.031 [0.869 – 1.224], P = .724). As the hypothesis of homogeneity had to be rejected (Q (1) = 40.077, P < .001), moderator analyses followed. Here, none of the variables under investigation turned out to be of importance (see Supplementary Table S8).

Focusing on full-time vs. part-time employment, four studies [42, 61, 64, 65] did not yield any associations, whereas results of Hill and colleagues [58] and Haas [66] pointed to full-time employment or more maternal working hours being linked to more EBP. Analyses of Brooks-Gunn and colleagues [16] again emphasised the importance of ethnicity. In White children some evidence pointed to full-time employment being associated with higher levels of EBP, whereas this was shown for part-time employment in Black children instead. A meta-analysis including three studies [16, 49, 65] indicated no association of maternal employment and EBP based on the random-effects model (OR = 1.271 [0.816 – 1.980], P = .289). However, under the fixed-effects model working full-time was associated with more EBP (OR = 1.119 [1.010 – 1.239], P < .05; see Figure 2). As the hypothesis of homogeneity had to be rejected (Q (1) = 15.147, P < .01), moderator analyses followed. None of the variables under investigation turned out to be of importance (see Supplementary Table S8).

Further three studies [17, 57, 67] focused on employment duration with a single study finding more months of employment (within the same job) being associated with less EBP [17]. A meta-analysis based on all three studies indeed indicated an association of maternal employment duration and EBP based on the fixed-effects model (r = .038 [.018 – .058], P < .001), albeit pointing to longer employment being associated with more EBP instead (see Figure 2). Under the random-effects model no association emerged (r = .012 [-.071 – .095], P = .777). The hypothesis of homogeneity had to be rejected (Q (1) = 28.105, P < .001), but due to the small number of studies included, no moderator analyses followed.

Four studies [16, 42, 58, 59] included further analyses on timing of return to work often pointing to early return, i.e., within the first year postpartum, being associated with more EBP [16, 42, 59]. As these analyses were hardly comparable to each other, no meta-analysis followed.

Aggression. Comparing children of employed and unemployed mothers, three out of five studies [68-72] pointed to employment being associated with more aggression [68, 70, 71]. However, the opposite was found as well [70, 71], especially under higher levels of social support received by mothers. A meta-analysis including four studies [68-71] did not yield a summary effect, neither under the random-effects model (OR = 1.168, P = .548) nor under the fixed-effects model (OR = 0.865, P = .108). As the hypothesis of homogeneity had to be rejected (Q (1) = 15.251, P < .01), moderator analyses followed with none of the variables under investigation turning out to be of importance (see Supplementary Table S8).

Whitaker and colleagues [73] focused on the association of employment duration and aggression. Here, no associations were obtained.

Hyperactivity/inattention. Four studies [39, 59, 70, 74] compared children of employed and unemployed mothers. Lekfuangfu and colleagues [59] detected maternal full-time employment to be linked to more hyperactivity/inattention but analyses of Nomaguchi [70] yielded some evidence of part-time (part-year) employment being associated with less hyperactivity instead. Here, in a meta-analysis including three studies [59, 70, 74] no summary effect emerged, neither under the random-effects model (OR = 1.041, P = .261) nor under the fixed-effects model (OR = 0.956, P = .664) The hypothesis of homogeneity had to be rejected (Q (1) = 12.437, P > .01), but due to the small number of studies included, no moderator analyses followed.

Focusing on full-time vs. part-time employment, Hadzic and colleagues [75] found 35–40 maternal weekly working hours to be directly linked to more hyperactivity/inattention when compared to 16–34 working hours. Under consideration of maternal parenting practices as mediating variables further indirect effects emerged linking 1–15 and more than 40 working hours to less hyperactivity/inattention. A meta-analysis including two studies [70, 75] indeed indicated an association of maternal employment and hyperactivity/inattention based on the fixed-effects model (OR = 2.677 [2.222 – 3.226], P < .001). Here, working full-time was linked to more hyperactivity/inattention (see Figure 2). Under the random-effects model no summary effect emerged (OR = 3.003 [0.305 – 29.571], P = .346). The hypothesis of homogeneity had to be rejected (Q (1) = 149.022, P < .001), but due to the small number of studies included, no moderator analyses followed.

A further analysis on employment duration did not yield any associations [73]. The same holds true for studies focusing on timing of return to work [59, 74]. As these analyses were hardly comparable to each other, no meta-analysis followed.

Conduct problems. Comparing children of employed and unemployed mothers, one out of two studies [59, 74] found full-time employment to be linked to more conduct problems [59]. A meta-analysis including both studies indeed yielded a summary effect based on the random-effects model (OR = 1.180 [1.055 – 1.320], P < .01) and the fixed-effects model (OR = 1.168 [1.086 – 1.257], P < .001). Employment was linked to more conduct problems (see Figure 2). As the hypothesis of homogeneity could not be rejected (Q (1) = 2.147, P = .143), no moderator analyses followed.

Focusing on full-time vs. part-time employment, Hadzic and colleagues [75] found 1-15 and more than 40 weekly working hours to be indirectly linked to less conduct problems when compared to 16–34 working hours. In terms of return to work analyses yielded mixed results. Lekfuangfu and colleagues [59] found some evidence of early return, i.e., within months seven to 12 postpartum, to be associated with more conduct problems. However, results of Lombardi and Coley [74] pointed to an association with later return instead, i.e., between months 9 to 24 postpartum, especially when working part-time and with increasing household income. However, this link was no longer present when further potentially mediating variables were included into the model. As these analyses were hardly comparable to each other, no meta-analysis followed.

Internalizing behavior problems

Overall internalizing behavior problems. Of five studies comparing children of employed and unemployed mothers [56, 58, 59, 62, 63], only Im and Vanderweele [63] found results linking employment to more IBP (especially in cases of absent or low paternal involvement). Employment was associated with less IBP under high paternal involvement instead. A meta-analysis including two studies [58, 59] verified the impression of no association under the random-effects model (OR = 0.922 [0.798 – 1.065], P = .268). However, under the fixed-effects model a summary effect emerged (OR = 0.896 [0.836 – 0.962], P < .01), indicating that children of employed mothers exhibited less IBP (see Figure 2). As the hypothesis of homogeneity could not be rejected (Q (1) = 2.98, P = .08) no moderator analyses followed.

Focusing on full-time vs. part-time employment, in three studies no interpretable results emerged [58, 64, 65], replicated by a meta-analysis including two studies [58, 65] both under the random-effects model (OR = 1.068 [0.925 – 1.234], P = .369) and the fixed-effects model (OR = 1.068 [0.925 – 1.234], P = .369). As the hypothesis of homogeneity could not be rejected (Q (1) = 0.031, P = .860) no moderator analyses followed.

Further two studies focused on employment duration with limited evidence pointing to more IBP in children of mothers unemployed longer [17, 67]. A meta-analysis including these studies was conducted with the random-effects model yielding no summary effect (r = -.075 [-.220 – .073], P = .318). However, under the fixed-effects model being employed longer was linked to less IBP (r = -.072 [-.103 – -.040], P < .001; see Figure 2). Albeit the hypothesis of homogeneity had to be rejected (Q (1) = 21.764, P < .001), due to the small number of studies included, no moderator analyses followed.

In terms of return to work analyses of Lekfuangfu and colleagues [59] included some evidence that returning within months 13–18 postpartum may be associated with less IBP when compared to not having returned to work by 18 months postpartum. Hill and colleagues [58] could not obtain any associations instead. As these analyses were hardly comparable to each other, no meta-analysis followed.

Anxiety and depressive symptoms. In terms of employment status, only a single study [70] out of five in total [43, 57, 69, 70, 72] included some evidence of less anxiety among children of employed mothers. A meta-analysis based on two studies [69, 70] indeed yielded no summary effect, neither under the random-effects model (OR = 0.837 [0.694 – 1.009], P = .062) nor under the fixed-effects model (OR = 0.837 [0.697 – 1.004], P = .055). As the hypothesis of homogeneity could not be rejected (Q (1) = 1.057, P = .304), no moderator analyses followed.

Further two studies focused on employment duration [57, 73] with only Whitaker and colleagues [73] finding children of mothers employed shorter to have higher odds of exhibiting problematic anxious/depressed behavior. No meta-analysis was conducted as respective outcomes were considered to be not similar enough to be combined.

Other internalizing symptoms. Lekfuangfu and colleagues [59] investigated emotional and peer problems not finding any differences among children of employed and unemployed mothers. However, having returned to work by 7–12 months postpartum was linked to less emotional and peer problems when compared to not having returned to work by 18 months postpartum. Osborne and Knab [69] focused on withdrawn behavior also not finding any differences among children of employed and unemployed mothers.

Prosocial behavior

Comparing children of employed and unemployed mothers, four out of seven studies [39, 49, 57, 59, 70, 74, 75] yielded at least some evidence for more PB in children of employed mothers [39, 49, 70, 75]. However, in a meta-analysis including five studies [49, 57, 59, 70, 74] no summary effect emerged, neither under the random-effects model (OR = 0.997 [0.785 – 1.266], P = .979) nor under the fixed-effects model (OR = 1.020 [0.973 – 1.068], P = .413). As the hypothesis of homogeneity had to be rejected (Q (1) = 94.522, P < .001) moderator analyses followed (see Supplementary Table S8). At sample-level, marital status was of importance (Q (1) = 3.96, P < .05). When compared to (majority) coupled samples mixed marital status was associated with a smaller effect size (b = -0.179, P < .05). Here, being employed was linked to less PB.

Focusing on full-time vs. part-time employment, Hadzic and colleagues [75] found indirect links of 1–15 maternal weekly working hours and more PB as well as of more than 40 hours and less PB when compared to 16–34 working hours. In analyses of Gassman-Pines [64] more working hours during nights were linked to less positive behavior (especially on weekends). A meta-analysis including two studies [49, 70] did not yield a summary effect, neither under the random-effects model (OR = 0.979 [0.789 – 1.216], P = .850) nor under the fixed-effects model (OR = 1.027 [0.927 – 1.138], P = .610). As the hypothesis of homogeneity could not be rejected (Q (1) = 2.522, P = .112), no moderator analyses followed.

Further two studies [57, 67] focused on employment duration with limited evidence pointing to less PB in children of mothers being unemployed longer [67]. A meta-analysis including these studies yielded a summary effect under the fixed-effects model (r = .023 [.000 – .047], P < .05), linking longer employment to more PB (see Figure 2), whereas under the random-effects model no summary effect emerged (r = .047 [-.054 – .147], P = .362). The hypothesis of homogeneity had to be rejected (Q (1) = 14.391, P < .001), but due to the small number of studies included, no moderator analyses followed.

In terms of return to work analyses included some evidence of early return, i.e., within the first year postpartum, to be associated with less PB [59, 74]. As these analyses were hardly comparable to each other, no meta-analysis followed.

Discussion

This systematic review with meta-analysis aimed at summarizing recent evidence on the association of maternal employment and mental health of children 0–7 years of age. We focused on employment status, working amount, employment duration, and timing of return to work and ran analyses for every single indicator of child mental health found, if possible. Generally, meta-analytic evidence pointed to only few associations of maternal employment and child mental health dependent on operationalizing of maternal employment and the outcome under investigation. Moderator analyses yielded even fewer results but were often hampered by small numbers of studies included.

Employment status. Single studies provided evidence of employment status being linked to somewhat less BP and more PB, but also more aggression. However, quantitative syntheses did not point to any associations here. Being employed instead turned out to be linked to more conduct problems but less IBP. Both analyses predominantly included children 5–7 years of age with maternal employment pertaining to the first years postpartum. When discussing why maternal employment could be associated with less problematic internalizing but more problematic externalizing behavior child care could mark a possible explanation. Children of working mothers are generally more likely to be placed in (nonmaternal) child care [76] and spend more time in such care arrangements [16] which has been found to be associated with child behavior especially in terms of more EBP [77-79]. Limited evidence also points to a possible link to less IBP instead [77]. Time spent with other children may be a potential mechanism and could both be detrimental and beneficial [79], e.g., by being exposed to more anti- or prosocial peer behavior when being placed in child care for more hours [80].

Further meta-analyses not yielding any summary effects may pertain to the inconclusive evidence included, especially in analyses focusing on BP or externalizing behavior, i.e., overall EBP, aggression, and hyperactivity/inattention. Marked heterogeneity emphasises the importance of considering moderators, e.g., data source. In US data maternal employment was associated with more BP whereas in a British sample being employed was linked to less BP instead. As both countries share quite comparable maternal employment rates with mothers working being the norm [81], our results point to regional or even cultural differences in the importance of maternal employment for child mental health. Compared to the US employment conditions in various European countries seem to be more supportive of mothers by providing more generous maternal leave entitlements [82]. Longer maternal leave has been shown to benefit maternal mental health [e.g., 83] which in turn is associated with better child mental health [20]. Furthermore, beside employment per se, as our meta-analytic evidence revealed actual working amount seems to be of importance with full-time employment being associated with more EBP and more hyperactivity/inattention. In the US mothers mostly work full-time whereas part-time work is more frequent in some European countries, e.g., the United Kingdom, Germany, or Switzerland [81]. Regional differences in the association of maternal employment and child mental health are further underlined by ethnicity constituting a moderator. The importance of this variable was already underlined by Berger and colleagues [47]. In their analyses, maternal employment was found to be beneficial for Black children whereas in Hispanic children a negative association emerged even under consideration of selection into employment (in White children no association was found). Among others, factors such as socioeconomic status, job characteristics, and parenting may be possible explanations. For instance, Black mothers seem to exhibit more harsh parenting behavior than White mothers do [84], which in turn has shown to be associated with problem behavior in children [e.g., 85, 86]. Employment and care by others then could compensate for that.

In terms of PB no summary effect emerged as well. However, maternal marital status was seen as moderator. In samples including a significant amount of lone mothers employment was linked to less PB. Hence, findings of a former meta-analysis [23] that underscored the importance of family structure for the association of employment and problem behavior are expanded by showing that family structure could be essential for the link to positive behavior as well. Possible mechanisms may include family income which has been shown to be linked to child mental health problems [87] and often is substantially lower in one-parent families.

Full-time vs. part-time employment. Limited evidence was found for full-time employment being linked to more EBP and more hyperactivity/inattention (which for the latter has to be interpreted with caution as results were mainly driven by large effects found in a single study). Both full-time and part-time working mothers share the advantages of being employed, e.g., increased financial resources [16] and better maternal (mental) health [88, 89] constituting factors in turn closely linked to child mental health [20, 87]. However, the role of time in child care (with the potential need of full-time working mothers to place their children in child care for even more hours) has already been discussed. Further studies found maternal sensitivity to be higher among part-time working mothers [maybe attributable to selection effects; 16, 90] which in turn is negatively associated with EBP [91]. Once more, at least in US data ethnicity could be of importance as well with Brooks-Gunn and colleagues [16] finding full-time employment to be linked to more EBP in White children whereas in Black children part-time employment was associated with more EBP instead. Unfortunately, due to the small number of studies included we were not able to include ethnicity in moderator analyses focusing on EBP.

Further meta-analyses not yielding any summary effects may pertain to differing definitions of full-time and part-time employment across studies. In general, heterogeneity played a smaller role compared to analyses on employment status with identifying moderators in terms of BP only. Here, adjustment turned out to be of importance. Often, when controlling for selection into employment by, e.g., inclusion of maternal education as covariate, differences in child mental health dependent on maternal employment turn out to be no longer present. However, we found full-time employment to be linked to BP when focusing on adjusted results. Therefore, other factors than maternal age, marital status, or mental health closely linked to employment [e.g., 16] and child mental health [e.g., 20] have to explain this interesting finding. We already discussed the potential roles of child care and parenting in this context.

Employment duration. Single analyses underscored an association of employment stability and child mental health. Longer employment duration turned out to be linked to less BP, less IBP, and more PB. Again, financial security or income may reflect underlying mechanisms. Employment stability also seems to be of importance for employees’ mental health [92] with the clear association of maternal and child mental health already having been discussed. Job churning or job loss may also be linked to less stability in child care arrangements with evidence indicating the importance of the latter for child mental health [76]. Despite that, longer employment duration was also associated with more EBP albeit included studies pointed to a missing or even negative link. The hypothesis of homogeneity had indeed to be rejected but due to the small number of studies included, again no moderator analyses followed. Once more, child care could mark a possible mechanism with children of mothers employed longer cumulatively spending more time in child care which has been associated with more EBP [78]. However, before actually resolving conflicting evidence more research on the association of maternal employment duration and EBP is highly warranted.

Return to work. Only few studies focused on timing of maternal employment rendering any meta-analysis impossible. However, qualitative syntheses indicated early maternal return to work, i.e., within the first 12 months postpartum, to be associated with worse child mental health, i.e., more EBP and less PB. For the latter, this may seem inconsistent with conclusions drawn for employment duration as analyses of Herbst [57] focusing on employment duration within the first 9 months postpartum could not unravel any cumulative negative link of employment and PB. It shall be noticed that by employment duration looking at how stably a mother is employed, even early after birth, and return-to-work analyses investigating when a mother best resumes employment it is all about two distinct variables. However, one could assume that potential detrimental effects of returning to work early may be offset if that employment is stable at least. Unfortunately, as both analyses relied on only two studies the evidence is too scarce to draw any final conclusions here.

Early return to work being linked to worse child mental health in terms of more EBP replicates evidence found for employment status as investigations yielding maternal employment being linked to more EBP mainly focused on employment within the first year postpartum. Less PB among children of mothers returning to work early could also be brought in accordance with the positive link detected for maternal employment and PB, i.e., being employed is associated with more PB, as most studies here concentrated on employment later in children’s life.

Indeed, prior investigations discussed early return controversially. Policies on family leave, including both maternal and paternal leave, are closely linked to timing of return to work. The positive association of maternal leave and maternal mental health [e.g., 83] has already been discussed and in turn, maternal and child mental health are closely linked to each other [20]. Besides that, many countries are now offering paternal leave as well, however, the actual use by fathers is low [93] albeit it already has been shown to be detrimental for maternal mental health if no paternal leave is taken by the respective partner [83]. Hence, negative associations of mothers’ early return to work and child mental health may be buffered in case paternal leave is utilised instead. However, this needs further research. Shorter durations of breastfeeding due to early return to work [94] constitute another potential mechanism as some evidence indicates a positive association of breastfeeding and child mental health [95, 96]. Again, child care may pose an explanation as well. When mothers return to work earlier children may have to start child care at younger ages. Especially attendance of child care within the first year postpartum has been shown to be negatively associated with child behavior [97].

Summary. Our findings suggest that whether maternal employment is associated with child mental health strongly depends on the operationalization of maternal employment, the outcome under investigation, and study/sample characteristics. Especially part-time employment, longer employment duration, and return to work after the first year postpartum may be beneficial for child mental health. Moderator analyses further especially pointed to regional differences in the association of maternal employment and child mental health.

Strengths and limitations

Previous research on the association of maternal employment and child mental health was limited by focusing solely on broader measures of maternal employment, e.g., status or working amount, and child mental health, e.g., EBP or IBP. Moreover, evidence was obtained by often mixing results on different age groups, i.e., infants, children, and adolescents. These approaches may have resulted in mistakenly missing associations of maternal employment and child mental health. Strengths of this systematic review with meta-analysis therefore lie in its additional focus on employment duration and return-to-work analyses and in running analyses for every single indicator of child mental health found, if possible. Moreover, we only included studies investigating children 0–7 years of age to avoid subsuming study results basically hard to compare and concentrated on very recent evidence on the variables’ of interest association. Special attention was further given to the investigation of moderators. Additional strengths include the systematic literature search as well as the standardized procedures of data extraction and assessment of study quality done by two reviewers independently.

However, some limitations need to be considered as well. First, despite the clear focus on young children, included studies were still characterized by high levels of heterogeneity underlined by most moderator analyses. Unfortunately, as often only few studies could be implemented in meta-analyses, we were not able to fully explain this heterogeneity. Even in case moderator analyses were run we may have missed further important variables here. Second, especially analyses on employment duration and subordinate measures of externalizing and internalizing behavior were often hampered by few studies focusing on them. As a compromise, we also considered summary effects based on the fixed-effects model. However, our analyses here may be seen as explorative. Third, models comparing full-time and part-time employment may further be hampered by single studies not sharing unique definitions of these categories. Studies also considered different sets of control variables and relied on different analytical techniques. Fourth, generalizability of findings is further hampered by most included studies stemming from the Western world (US in particular). Even here, moderator analyses pointed to regional differences in the association of maternal employment and child mental health. Differences in the normativity of full-time or part-time work and employment conditions mark possible explanations. Finally, we only focused on maternal employment. Hence, no conclusions on the association of paternal employment or leave-taking and child mental health can be drawn.

Outlook

Practical implications pertain to the endorsement of maternal employment per se and employment stability in particular especially after the first year postpartum as return-to-work analyses often demonstrated that working early after birth is associated with worse child mental health. Here, more generous maternal leave policies are warranted granting paid leave covering the first year postpartum. As first results already pointed to the importance of family leave, e.g., by demonstrating links to maternal mental health [83] with results of Liu and colleagues [98] showing an immediate association of shared parental caregiving and child behavior, further recommendations pertain to an expanded offer of paternal leave as well and promotion of its actual use. In terms of full-time employment being linked to worse child mental health, buffering factors warrant consideration. Examples include support of maternal sensitivity, e.g., through specific interventions, and enhancement of child care quality.

Implications for future research pertain to study methodology, populations, interventions, and outcomes under investigation. At study level, more investigations outside of the US are warranted utilizing, e.g., adequate analytical strategies, a comparable set of control variables, and consistent definitions of full-time and part-time employment. Especially in terms of single subordinate measures of child mental health such as conduct problems or anxiety and depressive symptoms is highly warranted before drawing conclusions here. This also accounts for analyses on employment duration and return to work with special focus on any interdependence among these two variables. Implications of the COVID-19 pandemic for the association of maternal employment and child mental health may be of further interest for future research. Here, already altered gender role attitudes on maternal employment [99] or employment conditions, e.g., working from home [100], may pose potential mechanisms. In terms of systematic investigations, further research should focus on associations in children aged 8 years and above to ensure whether maternal employment is differently linked to child mental health in infancy, childhood, or adolescence. Here, special focus could be given to the investigation of potential logged associations [24] and further subgroup analyses shedding light on additional important moderators. The systematic investigation of any association of child mental health and other employment factors than those investigated here, e.g., number of jobs held and job quality, falls below this point. Furthermore, systematic investigations focusing on an aggregated measure of parental employment instead of maternal conditions only could be promising. By doing so more knowledge on when and how children do benefit from (maternal) employment is generated enabling the derivation of further implications for practice.

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Table

Table 1. Study characteristics

Characteristic			k	%
Publication source^a
	Journal article		33	80.5
	Thesis		3	7.3
	Working paper		2	4.9
	Book chapter		1	2.4
	Discussion paper		1	2.4
	Monography		1	2.4
Data source^a
	US		26	63.4
		ECLS-B	6
		FFCWS	6
		NLSY79	3
		NICHD-SECCYD	2
		CCDP	1
		IDP	1
		PHDCN	1
		other	6
	Australia		4	9.8
		LSAC	3
		other	1
	United Kingdom		3	7.3
		MCS	2
		ALSPAC	1
	Denmark		2	4.9
		DALSC	2
	Canada		1	2.4
		NLSCY	1
	Germany		1	2.4
		ENEPS	1
	Indonesia		1	2.4
	Iran		1	2.4
	Japan		1	2.4
	South Korea		1	2.4
Intervention
	Employment status (incl. working amount)		34
	Employment duration		8
	Return to work		6
Outcome
	Behavior problems		15
	Externalizing behavior problems		26
		Aggression	6
		Hyperactivity/inattention	6
		Conduct problems	3
	Internalizing behavior problems		15
		Anxiety and depressive symptoms	6
		Other	2
	Prosocial behavior		9
Design
	Longitudinal		20	48.8
	Cross-sectional analyses only		21	51.2
Risk of bias^a
	Low		4	9.8
	Moderate		10	24.4
	High		27	65.9

Characteristic		k	%
Child age at outcome assessment (in years)
	0–1	1
	2	4
	3	10
	4	16
	5	9
	6	7
	7	2
Timing of maternal employment
	0–12 months	22
	13–23 months	12
	2 years	11
	3 years	8
	4 years	17
	5 years	7
	6 years	1
Ethnicity
	Mixed	17	41.5
	(Majority) White	6	14.6
	(Majority) Black	3	7.3
	n/a	15	36.6
Marital status^a
	Mixed	13	31.7
	(Majority) coupled	20	48.8
	(Majority) single	4	9.8
	n/a	4	9.8
ECLS-B = Early Childhood Longitudinal Study – Birth Cohort; FFCWS = Fragile Families and Child Wellbeing Study; NLSY79 = National Longitudinal Survey of Youth; NICHD-SECCYD = National Institute of Child Health and Human Development Study of Early Child Care and Youth Development; CCDP = National Impact Evaluation of the Comprehensive Child Development Program; IDP = Interactional and Developmental Processes Study; PHDCN = Project on Human Development in Chicago Neighborhoods; LSAC = Growing up in Australia, the Longitudinal Study of Australian Children; MCS = Millennium Cohort Study; ALSPAC = Avon Longitudinal Study of Parents and Children; DALSC = Danish Longitudinal Survey of Children; NLSCY = National Longitudinal Survey of Children and Youth; ENEPS = Erlangen-Nürnberger Entwicklungs- und Präventionsstudie (Erlangen-Nuremberg Development and Prevention Study); n/a = not available/applicable. ^aValues do not add up to 100% due to rounding.