https://orcid.org/0000-0002-4130-468X
Figures
Abstract
Background
Parents are the primary caregivers of young children. Responsive parent–child relationships and parental support for learning during the earliest years of life are crucial for promoting early child development (ECD). We conducted a global systematic review and meta-analysis to evaluate the effectiveness of parenting interventions on ECD and parenting outcomes.
Methods and findings
We searched MEDLINE, Embase, PsycINFO, CINAHL, Web of Science, and Global Health Library for peer-reviewed, published articles from database inception until November 15, 2020. We included randomized controlled trials (RCTs) of parenting interventions delivered during the first 3 years of life that evaluated at least 1 ECD outcome. At least 2 reviewers independently screened, extracted data, and assessed study quality from eligible studies. ECD outcomes included cognitive, language, motor, and socioemotional development, behavior problems, and attachment. Parenting outcomes included parenting knowledge, parenting practices, parent–child interactions, and parental depressive symptoms. We calculated intervention effect sizes as the standardized mean difference (SMD) and estimated pooled effect sizes for each outcome separately using robust variance estimation meta-analytic approaches. We used random-effects meta-regression models to assess potential effect modification by country-income level, child age, intervention content, duration, delivery, setting, and study quality. This review was registered with PROSPERO (CRD42018092458 and CRD42018092461). Of the 11,920 articles identified, we included 111 articles representing 102 unique RCTs. Pooled effect sizes indicated positive benefits of parenting interventions on child cognitive development (SMD = 0.32, 95% CI [confidence interval]: 0.23, 0.40, P < 0.001), language development (SMD = 0.28, 95% CI: 0.18 to 0.37, P < 0.001), motor development (SMD = 0.24, 95% CI: 0.15 to 0.32, P < 0.001), socioemotional development (SMD = 0.19, 95% CI: 0.10 to 0.28, P < 0.001), and attachment (SMD = 0.29, 95% CI: 0.18 to 0.40, P < 0.001) and reductions in behavior problems (SMD = −0.13, 95% CI: −0.18 to −0.08, P < 0.001). Positive benefits were also found on parenting knowledge (SMD = 0.56, 95% CI: 0.33 to 0.79, P < 0.001), parenting practices (SMD = 0.33, 95% CI: 0.22 to 0.44, P < 0.001), and parent–child interactions (SMD = 0.39, 95% CI: 0.24 to 0.53, P < 0.001). However, there was no significant reduction in parental depressive symptoms (SMD = −0.07, 95% CI: −0.16 to 0.02, P = 0.08). Subgroup analyses revealed significantly greater effects on child cognitive, language, and motor development, and parenting practices in low- and middle-income countries compared to high-income countries; and significantly greater effects on child cognitive development, parenting knowledge, parenting practices, and parent–child interactions for programs that focused on responsive caregiving compared to those that did not. On the other hand, there was no clear evidence of effect modification by child age, intervention duration, delivery, setting, or study risk of bias. Study limitations include considerable unexplained heterogeneity, inadequate reporting of intervention content and implementation, and varying quality of evidence in terms of the conduct of trials and robustness of outcome measures used across studies.
Conclusions
Parenting interventions for children during the first 3 years of life are effective for improving ECD outcomes and enhancing parenting outcomes across low-, middle-, and high-income countries. Increasing implementation of effective and high-quality parenting interventions is needed globally and at scale in order to support parents and enable young children to achieve their full developmental potential.
Author summary
Why was this study done?
- Parenting interventions have been underscored as a key strategy for improving early child development (ECD) outcomes.
- Although there are several existing reviews regarding the effectiveness of parenting interventions for improving ECD outcomes, prior reviews have focused narrowly on select types of parenting interventions, evaluated impacts on single ECD domain outcomes, included studies in either only high-income countries (HICs) or low- and middle-income countries (LMICs), and have not adequately explored treatment heterogeneity and potential moderators.
What did the researchers do and find?
- We conducted a systematic review and meta-analysis of 102 randomized controlled trials of parenting interventions for children during the first 3 years of life that were implemented across a total of 33 countries.
- We found that parenting interventions improved early child cognitive, language, motor, socioemotional development, and attachment and reduced behavior problems. Parenting interventions additionally improved parenting knowledge, parenting practices, and parent–child interactions. However, they did not significantly reduce parental depressive symptoms.
- We found that parenting interventions had significantly greater effects on child cognitive, language, and motor development and parenting practices in LMICs than HICs (e.g., effect on cognitive development was 3 times greater in LMICs versus HICs). Parenting interventions that included content on responsive caregiving had significantly greater effects on child cognitive development, parenting knowledge, parenting practices, and parent–child interactions than interventions that did not include content on responsive caregiving (e.g., effect on parenting practices was nearly 4 times greater for interventions with responsive caregiving content versus those without responsive caregiving content).
- We uncovered substantial variation in program content and implementation characteristics across studies and considerable heterogeneity in pooled effect size estimates across nearly all evaluated outcomes.
What do these findings mean?
- To the best of our knowledge, this is the largest and most comprehensive global systematic review and meta-analysis that demonstrates the effectiveness of parenting interventions during the first 3 years of life on a wide range of ECD and parent-level outcomes.
- Parenting programs are needed globally to enhance parent–child relationships and promote the healthy development of children during the earliest years of life.
- Future research should unpack the observed variability in program components and implementation features used across parenting interventions and examine their associations with outcomes to inform improved delivery, effectiveness, and scale of parenting interventions for ECD.
Citation: Jeong J, Franchett EE, Ramos de Oliveira CV, Rehmani K, Yousafzai AK (2021) Parenting interventions to promote early child development in the first three years of life: A global systematic review and meta-analysis. PLoS Med 18(5): e1003602. https://doi.org/10.1371/journal.pmed.1003602
Academic Editor: Lars Åke Persson, London School of Hygiene and Tropical Medicine, UNITED KINGDOM
Received: September 23, 2020; Accepted: April 1, 2021; Published: May 10, 2021
Copyright: © 2021 Jeong et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are within the manuscript and its Supporting information files.
Funding: This work was funded by the World Health Organization (grant # APW-201931623 awarded to AKY). The funder had no role in study design, data extraction and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
Abbreviations: BSID, Bayley Scales of Infant and Toddler Development; CI, confidence interval; ECD, early child development; HICs, high-income countries; LMICs, low- and middle-income countries; PRISMA, Preferred Reporting Items for Systematic Reviews and Meta-Analysis; RCTs, randomized controlled trials; SMD, standardized mean difference
Introduction
Globally, an estimated 250 million children under aged 5 years (43%) are at risk of not achieving their developmental potential in the earliest years of life due to a host of nutritional, health, and psychosocial risks [1–3]. Promotive interventions are particularly important in the first 3 years of life when the developing brain is most sensitive to experiences and the environment [4]. While various types of interventions including nutrition and health can support healthy development, recent evidence has revealed that parenting interventions that include components to directly enhance early child learning or strengthen parent–child relationships are more effective for improving early cognitive, language, motor, and socioemotional development [5–7].
Parenting interventions are social and behavioral programs intended to improve caregivers’ knowledge, attitudes, practices, and skills in order to promote optimal early child development (ECD) [8]. Parenting interventions can encompass a range of interventions targeting various risks, behaviors, or aspects of parent–child relationships, including interventions that focus on stimulation [6], shared book reading [9], attachment and parental sensitivity [10,11], behavior management [12,13], positive discipline and maltreatment prevention [14,15], and parental mental health [16,17]. These different types of parenting interventions have consistently shown benefits across a wide age range of children, and especially during early childhood [5,18].
Despite a significant rise over the past decade in the implementation and quality of parenting interventions globally, there has not been a recent review comprehensively synthesizing the latest state of the literature. One of the most recent and relevant reviews on parenting interventions during early childhood was published by Britto and colleagues [5] as part of The Lancet 2017 series on ECD. This review found significant small-to-medium sized benefits of parenting interventions on child cognitive (standardized mean difference (SMD) = 0.36, n = 19 studies), motor (SMD = 0.13, n = 9), and socioemotional development (SMD = 0.35, n = 13). However, this evidence synthesis was based on a review of 3 selected reviews published in 2014 [19] and 2015 [6,20] that focused only on ECD but not parenting outcomes and was limited to studies in low- and middle-income countries (LMICs). Another relevant review by Jeong, Pitchik, and Yousafzai [21] investigated the effectiveness of stimulation interventions during the first 3 years of life on parent-level outcomes and documented significant medium-to-large benefits on maternal knowledge (SMD = 0.91, n = 6), parenting practices (SMD = 0.57, n = 10), and mother–child interactions (SMD = 0.44, n = 3). No significant effect was observed for reducing maternal depressive symptoms (SMD = −0.10, n = 9). Yet this prior review focused specifically on stimulation interventions, examined effects on parenting but not ECD outcomes, and was also limited to LMICs.
While these and other reviews have underscored positive effects of particular types of parenting interventions on ECD outcomes [22,23], an updated review is overdue and needed to improve our current understanding of the effectiveness of parenting interventions during early childhood and generalizability of the evidence base. Additionally, little attention has been given previously to the role of intervention implementation characteristics as potential moderators of program effects on child or caregiving outcomes. Considering the diversity of contexts and populations in which parenting programs are implemented, there is a need to investigate whether certain implementation factors are associated with differential program effectiveness.
Therefore, the present study aimed to provide a comprehensive global review of the effectiveness of parenting interventions delivered during the first 3 years of life on both ECD and parent-level outcomes. This study updates, synthesizes, and expands on previous reviews by (1) adopting an inclusive definition of parenting interventions as those that aim to improve caregiver interactions, behaviors, knowledge, beliefs, attitudes, or practices with their children in order to improve ECD; (2) focusing on interventions targeting caregivers and children during the first 3 years of life; (3) considering a broad set of both ECD and caregiver outcomes; and (4) including studies across low-, middle-, and high-income countries. The primary aim was to quantify the pooled effectiveness of parenting interventions delivered during the first 3 years of life on ECD and parenting-related outcomes. The secondary aim was to explore whether effects on ECD and parenting outcomes differed by country income level, child age, intervention content, duration, delivery, setting, and study quality.
Methods
Search strategy and selection criteria
This systematic review and meta-analysis was conducted and reported using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines [24] (S1 PRISMA Checklist). Six electronic bibliographic databases (MEDLINE, Embase, PsycINFO, CINAHL, Web of Science, and Global Health Library) were searched for articles published from database inception until May 15, 2019. The search was subsequently updated during the peer-review process to include articles published between May 16, 2019 to November 15, 2020. The search strategy (S1 Text) was informed by search terms and keywords used in prior systematic reviews related to parenting interventions [5,6,25] and through consultations with a research librarian. Reference lists of relevant studies and reviews were also scanned for any additional studies that may have been missed.
Full-text, peer-reviewed articles were included if they met the following criteria: (1) parenting interventions that aimed to improve interactions, behaviors, knowledge, beliefs, attitudes or practices of parents with their children in order to improve ECD; (2) evaluated using a randomized controlled study design; (3) targeted children and their parents during early childhood (pregnancy through the first 3 years of life); and (4) measured at least 1 ECD outcome after the completion of the intervention (or shortly thereafter). In this study, parents are broadly defined as the legal guardian, biological parent, or adult caregiver responsible for the well-being of the child [20]. Studies were excluded if they met any of the following criteria: (1) not a relevant parenting intervention focused on promoting ECD; (2) nonrandomized study design (e.g., quasi-experimental studies); (3) targeted a population of children who were, on average, older than 36 months; (4) targeted a population of children or parents who had a diagnosed illness or disability; and/or (5) did not measure at least 1 ECD outcome.
Titles and abstracts of all identified articles were independently screened by at least 2 reviewers (JJ, EF, and a team of graduate research assistants). If the title and abstract screening was insufficient for determining eligibility, the full-text article was reviewed for eligibility criteria. Any discrepancies between the 2 reviewers regarding the eligibility of a study were resolved through discussions among the reviewers, with input from another author (AKY) as needed until consensus was reached.
For studies meeting the eligibility criteria, full-text articles were reviewed. Data were extracted by JJ, EF, and a team of trained graduate research assistants using a prepiloted extraction form. JJ and EF trained the graduate research assistants over the course of a 3-week training period on how to use the data extraction sheet based on pilot exercises of relevant articles. Throughout the entire data extraction process, each data extraction completed by the research assistants was independently extracted by a second reviewer (JJ or EF), and any issues were discussed and resolved during the weekly in-person team meetings with the research assistants. For additional quality assurance, 35% of assigned articles were randomly selected for independent data extraction by a third reviewer (JJ or EF). Any discrepancies between the master reviewers (JJ and EF) regarding the extracted data were resolved through discussions and consensus together with an additional reviewer (AKY).
Outcomes
The primary outcomes were 6 domains of ECD: cognitive, language, motor, and socioemotional development, behavior problems, and attachment. These ECD outcome domains have been prioritized in previous work, commonly measured across global contexts, and are each unique aspects of child development during the first 3 years of life [26,27]. Moreover, each of these ECD outcome domains has shown predictive validity with later achievement, function, performance, or outcomes [27]. Measures of developmental disabilities (e.g., autism or ADHD) did not qualify as ECD outcomes. The secondary outcomes were 4 measures of parenting: parenting knowledge, parenting practices, parent–child interactions, and parental depressive symptoms.
Data analysis
Effect sizes on ECD and parenting outcomes were calculated as SMD between the intervention and comparison arms (e.g., no intervention, nonparenting intervention, standard of care), with respect to change in mean values from baseline to endline (when baseline values were reported) after standardization by their pooled standard deviation (SD). In multiarm studies, the comparison group was typically the intervention arm without any parenting components and/or the standard of care. For studies that reported outcomes from multiple follow-up waves of assessments, outcome measurements from the time point closest to the completion of the intervention were used for the analyses. The magnitude of effect sizes was interpreted in the context of public health, pediatric, and early education interventions and the practical significance with respect to the outcomes [28].
Each of the primary and secondary outcomes was examined in separate models. We used a robust variance estimation meta-analysis model [29] to account for multiple measurements per trial per outcome domain. This approach allows for the inclusion of any number of dependent effect size estimates from a given study to contribute to the pooled effect size estimate for an outcome, resulting in increased power and more precise estimates. For example, this approach was used to handle the separately reported effect sizes for receptive language and expressive language in a given study for overall language development or both internalizing and externalizing behaviors for overall child behavior problems. Pooled effect size estimates were based on random effects models. P values < 0.05 denoted statistical significance. Heterogeneity of the pooled effect size was assessed using the I2 statistic and the Cochran Q test and its P value.
Moderator analyses were conducted on all outcomes using random effects meta-regression models to explore potential sources of heterogeneity in the average effect by the following prespecified sample, intervention, and study characteristics: country-income level (LMICs or high-income countries (HICs)), average child age at baseline in months, whether the parenting intervention included a component to enhance responsive caregiving (see S1 Table for classification of responsive caregiving interventions) [25,30], intervention duration in months, delivery modality (individual, group, or both), setting (home, community, clinic, or combination), and study quality score. Study quality was assessed using the Cochrane Collaboration Risk of Bias Assessment Tool for randomized controlled trials (RCTs) [31]. Studies were rated as low risk (0 points), unclear risk (1 point), and high risk (2 points) for a total risk of bias score ranging from 0 to 16 [22,32]. For the continuous moderator variables, we generated a binary variable for child age at baseline and intervention duration (< or ≥12 months) and a binary study quality variable based on a mean split of the total risk of bias score (lower or higher risk of bias) and compared effect estimates according to these subgroups. Statistical significance for the moderator variables of country-income level, intervention content, delivery, and setting was determined from the Qbetween test statistic which was evaluated on the χ2 distribution. For the remaining moderator variables that were originally continuous measures (i.e., child age, intervention duration, and study quality score), statistical significance was determined from meta-regressions using the continuous measure (e.g., child age in months).
Publication bias was examined for each outcome analysis using the Egger’s regression test to test the null hypothesis of small-study bias (i.e., the extent to which less precise or smaller sample studies yield greater effects than larger sample studies) [33]. All analyses were conducted using Stata version 16. This review was preregistered with PROSPERO (CRD42018092458 and CRD42018092461). See S1 Protocol for the final review protocol used for the present study and notes regarding any changes made from the initial prospectively registered protocol.
Results
Study selection and inclusion
A total of 11,906 unique records were identified from electronic databases. Fourteen additional records were identified from article references and subject matter expertise. A total of 11,580 records were excluded based on title and abstract screening. The full texts of the remaining 340 articles were reviewed, and 229 articles were excluded for not meeting inclusion criteria. The final set comprised of 111 articles representing 102 unique RCTs (Fig 1).
Sample, intervention, and study characteristics
Table 1 presents the characteristics of the 102 RCTs of parenting interventions. Trials were implemented across a total of 33 countries. The majority of trials were conducted in HICs (61 trials in 14 countries), compared to LMICs (41 trials in 19 countries). The most represented countries were the United States of America (40 trials), Bangladesh (8 trials), Jamaica (6 trials), and India (5 trials). Studies were published between 1974 and 2020. Analytic sample sizes ranged from 32 to 3,202 individuals. The average age of children at baseline varied across interventions: 16 trials (16%) enrolled pregnant mothers, 30 (29%) enrolled children with an average age of 3 months and younger, 24 (24%) enrolled children with an average age of 3 to 12 months, and 32 (31%) enrolled children who were on average older than 12 months. Intervention duration ranged from a brief intervention delivered over 1 month to longer interventions delivered across the first 5 years of the child’s life. Nearly all interventions (93%) focused on supporting mothers exclusively, with only 7 interventions (7%) additionally engaging fathers to some degree [34–40].
Out of the total 102 interventions, 70 (69%) had some degree of a responsive caregiving component that aimed to improve parent–child interactions. Of these responsive caregiving interventions, 37 interventions (53%) involved facilitators who observed live parent–child interactions and/or utilized video recordings in order to provide feedback for promoting parental sensitivity and responsiveness in the context of play, communication, reading, and/or feeding. The other 33 responsive caregiving interventions (47%) more generally aimed to improve the quality of parent–child interactions through guidance, demonstrations, and encouragement of parents to practice during sessions and on their own.
The remaining 32 interventions (31%) did not include responsive caregiving components. Of these, 22 (69%) provided general parenting support with information and guidance on child development and parenting topics, and 10 (31%) focused on increasing parental stimulation and/or provision of learning materials. Among the total 102 interventions, 45 (44%) also integrated messages beyond parenting for ECD, such as maternal and child nutrition, child health, caregiver mental health, and early education.
Interventions utilized a range of delivery models: 58 interventions (57%) were delivered to individual caregivers and families, 13 (13%) were exclusively group based, and 31 (30%) incorporated both individually delivered and group-based components. Delivery settings also varied. Nearly half or 47 interventions (46%) were delivered exclusively through home visits, 11 in a clinical or hospital context (11%), 11 in a community space (11%), and 32 interventions (31%) used a combination of multiple settings. One intervention was delivered virtually.
Risk of bias assessment
The total risk of bias score across all studies was moderate (mean = 5.1, SD = 1.5) ranging from 2 to 9 on a scale of 0 to 16. In general, risk of bias was low for random sequence generation, blinding of outcome assessors, and incomplete outcome data (S1 Fig). However, risk of bias for allocation concealment and selective reporting were unclear for the majority of studies. Given the nature of psychoeducational and behavioral parenting interventions that involve parents’ active participation, blinding of participants was not possible. Egger’s tests suggested evidence of small-sample bias for 2 out of the 10 outcomes: child language development, z = 2.74, P = 0.01; and parent–child interactions, z = 3.78, P < 0.001.
Effects on early child development outcomes
Fifty-eight studies provided a total of 58 effect sizes for children’s cognitive development. Approximately half of these studies (56%) reported any details regarding reliability or validity of the measure of cognitive development. The Bayley Scales of Infant and Toddler Development (BSID) [41] was the most commonly used measure in more than half the studies (54%). See S2 Table for full list of measures used for each of the outcomes. The pooled result showed a moderate positive impact of parenting interventions on improving cognitive development (SMD = 0.32, 95% CI: 0.23, 0.40, P < 0.001; I2 = 89%, P < 0.001; Fig 2).
Blue squares represent the SMD for each study, with the size of the square being proportional to the study weight. The whiskers extending from each side of the square represent the range of the 95% CI. The green diamond shows the overall pooled effect size using a random-effects model, which is centered at the point estimate and the diamond width representing the 95% CI. SMD, standardized mean difference.
Forty-six studies provided a total of 58 effect sizes for children’s language development. Approximately half of these studies (57%) reported any details regarding reliability or validity of the measure of language development. The BSID (25%) and the MacArthur-Bates Communicative Development Inventory (14%) were the most commonly used measures. The pooled result showed a moderate positive impact on improving language development (SMD = 0.28, 95% CI: 0.18, 0.37, P < 0.001; I2 = 91%, P < 0.001; Fig 3).
Blue squares represent the SMD for each study, with the size of the square being proportional to the study weight. The whiskers extending from each side of the square represent the range of the 95% CI. The green diamond shows the overall pooled effect size using a random-effects model, which is centered at the point estimate and the diamond width representing the 95% CI. SMD, standardized mean difference.
Thirty-five studies provided a total of 45 effect sizes for children’s motor development. Approximately half of these studies (56%) reported any details regarding reliability or validity of the measure of motor development. The BSID was the most commonly used measure in more than half the studies (56%). The pooled result showed a moderate positive impact on improving motor development (SMD = 0.24, 95% CI: 0.15, 0.32, P < 0.001; I2 = 84%, P < 0.001; Fig 4).
Blue squares represent the SMD for each study, with the size of the square being proportional to the study weight. The whiskers extending from each side of the square represent the range of the 95% CI. The green diamond shows the overall pooled effect size using a random-effects model, which is centered at the point estimate and the diamond width representing the 95% CI. SMD, standardized mean difference.
Twenty-nine studies provided a total of 31 effect sizes for children’s socioemotional development. Nearly 2 in 5 studies (38%) reported any details regarding reliability or validity of the measure of socioemotional development. All measures were caregiver reported and most commonly included the Ages and Stages Questionnaire [42] (16%), Ages and Stages Questionnaire: Social-Emotional [43] (13%), and the Brief Infant–Toddler Social and Emotional Assessment [44] (13%). The pooled result showed a small positive impact on improving socioemotional development (SMD = 0.19, 95% CI: 0.10, 0.28, P < 0.001; I2 = 81%, P < 0.001; Fig 5).
Blue squares represent the SMD for each study, with the size of the square being proportional to the study weight. The whiskers extending from each side of the square represent the range of the 95% CI. The green diamond shows the overall pooled effect size using a random-effects model, which is centered at the point estimate and the diamond width representing the 95% CI. SMD, standardized mean difference.
Twenty-nine studies provided a total of 35 effect sizes for children’s behavior problems. Nearly half of the studies (47%) reported any details regarding reliability or validity of the measure of behavioral problems. All measures were caregiver reported, and the Child Behavior Checklist [45] was the most commonly used measure in more than half the studies (53%). The pooled result showed a small impact on reducing behavior problems (SMD = −0.13, 95% CI: −0.18, −0.08, P < 0.001; I2 = 53%, P < 0.001; Fig 6).
Blue squares represent the SMD for each study, with the size of the square being proportional to the study weight. The whiskers extending from each side of the square represent the range of the 95% CI. The green diamond shows the overall pooled effect size using a random-effects model, which is centered at the point estimate and the diamond width representing the 95% CI. SMD, standardized mean difference.
Eleven studies provided a total of 11 effect sizes for infant–caregiver attachment. The majority of studies (85%) reported any details regarding reliability or validity of the measure of attachment. The Ainsworth Strange Situation Procedure [46] was the most commonly used measure in 2 out of 5 studies (38%). The pooled result showed a moderate positive impact on improving attachment (SMD = 0.29, 95% CI: 0.18, 0.40, P < 0.001; I2 = 0%, P = 0.92; Fig 7).
Blue squares represent the SMD for each study, with the size of the square being proportional to the study weight. The whiskers extending from each side of the square represent the range of the 95% CI. The green diamond shows the overall pooled effect size using a random-effects model, which is centered at the point estimate and the diamond width representing the 95% CI. SMD, standardized mean difference.
Effects on parenting outcomes
Sixty-four studies (63%) measured at least 1 parenting outcome, and 35 studies (34%) measured 2 or more parenting outcomes. Sixteen studies provided a total of 16 effect sizes for parenting knowledge. Less than half of studies (44%) reported any details regarding reliability or validity of the measure of parenting knowledge. Nearly all studies (88%) used a knowledge questionnaire that was developed by the authors. The pooled result showed a large positive impact on improving parenting knowledge (SMD = 0.56, 95% CI: 0.33, 0.79, P < 0.001; I2 = 97%, P < 0.001; Fig 8).
Blue squares represent the SMD for each study, with the size of the square being proportional to the study weight. The whiskers extending from each side of the square represent the range of the 95% CI. The green diamond shows the overall pooled effect size using a random-effects model, which is centered at the point estimate and the diamond width representing the 95% CI. SMD, standardized mean difference.
Thirty-five studies provided a total of 40 effect sizes for parenting practices. Two-thirds of studies (66%) reported any details regarding reliability or validity of the measure of parenting practices. The Home Observation of Measurement of the Environment Inventory-Infant and Toddler version [47] was the most commonly used measure in more than half of studies (58%). The pooled result showed a moderate positive impact on improving parenting practices (SMD = 0.33, 95% CI: 0.22, 0.44, P < 0.001; I2 = 93%, P < 0.001; Fig 9).
Blue squares represent the SMD for each study, with the size of the square being proportional to the study weight. The whiskers extending from each side of the square represent the range of the 95% CI. The green diamond shows the overall pooled effect size using a random-effects model, which is centered at the point estimate and the diamond width representing the 95% CI. SMD, standardized mean difference.
Twenty-seven studies provided a total of 27 effect sizes for parent–child interactions. Three in four studies (77%) reported any details regarding reliability or validity of the measure of parent–child interactions. Nearly all studies directly observed and coded quality of mother–child interactions (91%). The pooled result showed a moderate positive impact on improving parent–child interactions (SMD = 0.39, 95% CI: 0.24, 0.53, P < 0.001; I2 = 93%, P < 0.001; Fig 10).
Blue squares represent the SMD for each study, with the size of the square being proportional to the study weight. The whiskers extending from each side of the square represent the range of the 95% CI. The green diamond shows the overall pooled effect size using a random-effects model, which is centered at the point estimate and the diamond width representing the 95% CI. SMD, standardized mean difference.
Twenty-four studies provided a total of 25 effect sizes for parental depressive symptoms. More than half of studies (59%) reported any details regarding reliability or validity of the measure of depressive symptoms. The Center for Epidemiologic Studies Depression Scale [48] was the most commonly used measure in 2 out of 5 studies (41%). The pooled result did not indicate a significant reduction in caregiver depressive symptoms (SMD = −0.07, 95% CI: −0.16, 0.02, P = 0.08; I2 = 76%, P < 0.001; Fig 11).
Blue squares represent the SMD for each study, with the size of the square being proportional to the study weight. The whiskers extending from each side of the square represent the range of the 95% CI. The green diamond shows the overall pooled effect size using a random-effects model, which is centered at the point estimate and the diamond width representing the 95% CI. SMD, standardized mean difference.
Moderator analyses
Given the large observed heterogeneity across all but one of the pooled effect size estimates, we conducted several moderator analyses to investigate potential sources of this heterogeneity. Tables 2 and 3 present the effects on ECD and parenting outcomes, respectively, stratified by the 7 characteristics: country-income level, average child age at baseline, intervention content, intervention duration, delivery, setting, and study quality. Parenting interventions had a greater effect on child cognitive, language, and motor development and parenting practices in LMICs compared to HICs, and the subgroup differences for these outcomes were statistically significant (e.g., effects on cognitive development: SMD = 0.41, 95% CI: 0.29, 0.53 in LMICs versus SMD = 0.17, 95% CI: 0.10, 0.22 in HICs; P < 0.001 for difference between subgroups; Table 2). Although effects on child socioemotional development, parenting knowledge, parent−child interactions, and parental depressive symptoms did not significantly differ by country-income level, the magnitudes of the estimates were consistently greater for all outcomes in LMICs versus HICs (Table 3).
Parenting interventions that promoted responsive caregiving had significantly greater effects on child cognitive development, parenting knowledge, practices, and parent–child interactions compared to interventions without responsive caregiving (e.g., effects on parenting practices: SMD = 0.42, 95% CI: 0.29, 0.56 for interventions with responsive caregiving components versus SMD = 0.11, 95% CI: 0.01, 0.22 for those without; P = 0.001 for difference between subgroups; Table 3). With the exceptions of greater subgroup effects on cognitive development for programs targeting children older than 12 months of age and greater effects on parenting practices for programs less than 12 months in duration, there were no other subgroup differences on any outcomes by child age, intervention duration, delivery, setting, or study risk of bias score (Tables 2 and 3).
Discussion
To the best of our knowledge, this is the largest and most comprehensive systematic review and meta-analysis that synthesized 102 parenting interventions delivered during early childhood from across 33 countries and estimated the effectiveness on a wide range of ECD and caregiving outcomes. We found that parenting interventions delivered during the first 3 years of life improved early child cognitive, language, motor, and socioemotional development, and attachment, and reduced behavior problems. Parenting interventions additionally improved parenting knowledge, parenting practices, and parent–child interactions; however, they did not significantly reduce parental depressive symptoms. Our findings extend prior evidence in 4 key ways.
First, previous reviews of parenting interventions delivered during early childhood have focused on the effectiveness of select types of parenting interventions on 1 or 2 developmental outcomes [6,49]. We conducted the most comprehensive synthesis that evaluates intervention effects on 6 distinct child development outcomes that are most relevant to children during the earliest years of life. Overall, pooled effect sizes were relatively greater for cognitive, language, and motor development and attachment, but smaller for socioemotional development and behavior problems. Greater estimated pooled effects on cognitive, language, and motor development are consistent with the strategies used in the majority of reviewed parenting interventions that focused largely on increasing early play and learning opportunities—such as through caregiver engagement in stimulation activities or enhanced verbal responsiveness—which are directly related to these particular outcomes. In contrast, the smaller observed effects on socioemotional development and behavior problems are likely because fewer of the reviewed parenting interventions incorporated program components directly related to the commonly assessed outcome domains such as emotional competence or externalizing problem behaviors.
In order to effectively improve child socioemotional development and reduce behavior problems, interventions require evidence-based curriculum content and strategies that are grounded in social learning theory, such as supporting caregivers’ behavioral management skills, addressing parental mental health, and encouraging nonviolent discipline [23,50]. Yet, most parenting programs for socioemotional and behavioral development to date have been commonly delivered for preschool-aged children rather than young children during the earliest years of life [23]. New intervention models are needed in order to more effectively improve early child socioemotional and behavioral development particularly for young children during infancy and early childhood. Part of this effort will require establishing standardized measurement tools for assessing socioemotional development and behavioral problems that can be used reliably and cross-culturally in the context of interventions with young children [51].
Second, we analyzed the impact of parenting interventions on parents themselves and found improvements in parenting knowledge, parenting practices, and parent–child interactions. However, 40% of studies aimed at improving ECD did not measure a single parenting outcome. Given that the primary focus of parenting interventions is to support parents and improve the caregiving environment, it is critical to measure parenting as a way of understanding how interventions impact ECD [21,52]. More mediation analyses are needed to empirically substantiate program theories of change and identify the key caregiving mechanisms by which parenting programs lead to improved ECD outcomes [36,53–55].
We found little evidence to support that parenting interventions reduced parental depressive symptoms. By covering a broader set of parenting interventions and including studies in HICs, our results extend the findings of a prior meta-analysis that found that stimulation interventions did not significantly reduce maternal depressive symptoms in LMICs [21]. This overall null effect on depressive symptoms is likely due to the fact that few of the parenting interventions had an explicit psychological component to address parental mental health. However, one notable exception was a parenting group intervention in Uganda that integrated sessions on not only stimulation and responsive caregiving but also parental emotion regulation, coping strategies, and principles of cognitive behavioral therapy. This intervention found medium-sized reductions in maternal depression [36]. While bundling multiple components together (e.g., mental health and parenting) to create intervention packages is recommended in the literature [5], additional research is needed to determine the independent and additive benefits of particular components (e.g., those that target mental health versus parenting) in order to optimize intervention effects on outcomes.
In spite of the observational evidence that fathers are critically important for ECD [56], only 7 parenting interventions in this review (7%) engaged fathers to some degree [34–40], and only 1 study measured paternal outcomes from fathers directly (who only comprised 5% of the respondents in this study) [39]. A prior review has drawn attention to the limited number of parenting interventions with fathers and the program implementation barriers that limit fathers’ participation in parenting interventions across global contexts [57]. More research is needed to determine how to optimize the design and delivery of parenting programs so that they are inclusive of fathers and can achieve benefits for maternal and paternal parenting and ECD [58].
Third, moderator analyses showed that parenting interventions had greater effects in LMICs compared to HICs for improving child cognitive, language, and motor development and parenting practices. Parents and children in LMICs are more likely to be exposed to additional risk factors that constrain nurturing care and ECD (e.g., low parental education, malnutrition, fewer early learning opportunities) [3,59], such that support for parenting may be more beneficial in low-resource contexts. More research is needed to understand whether and how variation in risk profiles within populations may influence the degree of benefits from a parenting intervention [60]. It is worth noting that none of the included studies directly compared the same intervention program in a LMIC and HIC. As a result, it is possible that these subgroup results may also, in part, be confounded by other differences in intervention design and implementation between LMICs and HICs.
Regarding intervention content, we found that those with responsive caregiving components had significantly greater impacts on child cognitive development, parenting practices, and parent–child interactions, compared to interventions that did not include responsive caregiving content. These results underscore the importance of not only increasing early play and learning materials (e.g., provision of homemade toys), which have traditionally been the focus of parenting intervention for young children especially in LMICs, but also incorporating program components that directly support parental sensitivity and responsiveness [25,61].
At the same time, we did not find evidence to suggest that child age, intervention duration, delivery modality, or setting moderated intervention effects on more than one outcome. The lack of statistically significant subgroup results by child age are consistent with the few prior meta-analyses that have similarly shown no age effects among parenting interventions focused during early childhood [9,22] or spanning broader age ranges from early to middle childhood [49] or birth to age 18 [62]. Despite strong neuroscience and economic arguments for intervening as early in life as possible [4,63], our review suggests that parental engagement and support programs may indeed have universal benefits on child and parent outcomes irrespective of child age or the timing of introduction.
Furthermore, the lack of statistically significant subgroup results by program duration, delivery modality, and setting are also consistent with the few prior meta-analyses that have conducted similar analyses and shown no associations between these program aspects and intervention effects on ECD and parent-level outcomes [62]. One recently published cluster RCT specifically compared the effectiveness of weekly home visits to weekly mother–child group sessions over a 2-year period in rural India [64]. Trial results revealed that group sessions were as effective as home visits in improving child cognition and language, and both delivery models similarly had null impacts on child motor, socioemotional, behavior development, and parenting knowledge and practices. Of note, cost analysis revealed that the group-based model required a quarter of the costs compared to home visiting. Nevertheless, our findings suggest that there are various effective implementation strategies and program models that can be used to deliver parenting interventions and achieve positive impacts on ECD and parent outcomes. Decisions regarding program duration, delivery modality, and setting should be determined based on the existing resources and systems, community needs, risk profiles of the population, and cultural context.
In summary, our study had several strengths. These include the comprehensive review of RCTs conducted in LMICs and HICs, the investigation of multiple child development and caregiver outcomes, the large number of studies and participants represented, and the various moderator analyses conducted to explore potential features associated with intervention effectiveness. At the same time, there are a number of limitations that should be noted. First, there was considerable unexplained heterogeneity in the pooled effects across outcomes. Future research should further explore heterogeneity in treatment effects by other program factors (e.g., content, theoretical goals, behavior change techniques) and intervention implementation features (e.g., dosage, fidelity, population risk profiles, supervision and training provided to delivery agents). Considering the generally inadequate reporting of intervention details that we identified across the majority of studies, future trials should use standardized guidelines such as CARE [65] and TIDieR [66] for common reporting of intervention content and implementation to facilitate more nuanced comparisons and subgroup analyses. Second, our review focused on parenting interventions for children during the first 3 years of life. As a result, other relevant parenting interventions with preschool-aged children [67,68] or those covering a broader age range of children (e.g., 2- to 6-year-olds) [69,70] were excluded, which limits the generalizability of our results. Third, the reporting of the psychometric properties of measures (e.g., reliability and validity evidence, adaptation procedures) was highly variable across studies, with many studies not reporting any such details. Measures of ECD and parenting ranged widely from validated and adapted assessments to unstandardized measures, which may affect comparability across studies and robustness of findings. Fourth, our meta-analysis involved 6 ECD outcomes and 4 parent-level outcomes and 7 moderator variables, which raises the issue of statistical multiplicity and the increased risk for false positive findings in our estimates of pooled effect sizes and subgroup analyses. Although we used robust variance estimation to address multiplicity and statistical dependencies, this method might raise issues of disproportionate influence from studies that contribute a large number of effect sizes relative to those that contribute fewer, and particularly when the overall number of studies and effect sizes is relatively small [71]. Future reviews should apply additional methods to address issues of multiplicity. Fifth, we found evidence suggesting small-sample bias for 2 outcomes (child language and parent–child interactions) based on the results of Egger’s tests. Future reviews should include searches of grey literature, regional databases, and in multiple languages to improve the global coverage and reduce publication bias in the evidence base.
Finally, our review also highlighted other broader issues with regard to risk of bias in the design, conduct, and reporting of parenting intervention trials. Specifically, the majority of trials had potential concerns of selection bias due to inadequate details about what methods were used to conceal the allocation sequence before assignment to determine whether intervention allocations could have been foreseen before or during enrolment. Additionally, the majority of trials were not preregistered and did not have a study protocol of prespecified outcomes to assess whether selective outcome reporting bias or selective analysis reporting bias was present. Selective reporting bias, especially of null results, may additionally contribute to the publication bias detected for some of the outcomes. In light of our findings, future trials of parenting interventions should preregister primary and secondary outcomes and their scoring methods in study protocols, report all analyzed outcomes regardless of statistical significance levels, and provide adequate descriptions in publications not only regarding random sequence generation but also the allocation concealment process to especially improve the quality of this body of evidence.
Conclusions
Parenting interventions during the first 3 years of childhood are effective for improving ECD and caregiving. In the last decade, there has been considerable policy attention on ECD globally [8]. The United Nation’s Sustainable Development Goal Target 4.2 is to ensure that all girls and boys have access to quality early childhood development, care, and education services [72]. However, the current policy landscape for ECD has not yet resulted in greater investments and implementation of large-scale national parenting programs. More implementation science research regarding how to adapt and deliver parenting programs across diverse local contexts, coordinate within existing systems and services, finance programs so that they are cost-effective and sustainable, and scale parenting programs while maintaining quality and effectiveness is needed to accelerate political will and action. Finally, while the present review supports robust immediate benefits of parenting interventions during early childhood, more follow-up studies of individual trials are needed to determine whether there are sustained, longer-term effects for children and caregivers over the life course [73]. Greater knowledge regarding the sustainability or fadeout of effects can guide the design and packaging of improved parenting programs, such as the integration of subsequent “booster” sessions that can potentially further support children and caregivers’ evolving needs and sustain intervention benefits over the life course.
Supporting information
S1 Table. Definition of parenting interventions and those that focus on responsive caregiving versus those that do not.
https://doi.org/10.1371/journal.pmed.1003602.s004
(DOCX)
S2 Table. Measures used for each ECD and parenting outcome domain.
https://doi.org/10.1371/journal.pmed.1003602.s005
(DOCX)
S1 Fig. Risk of bias across all randomized controlled trials.
https://doi.org/10.1371/journal.pmed.1003602.s006
(DOCX)
Acknowledgments
We thank Carol Mita, research librarian at the Francis A. Countway Library of Medicine at the Harvard Longwood Campus, for her assistance in the literature search. We thank the following graduate research assistants for their contributions to data extraction during an early stage of the study: Alastair Fung, Raghbir Kaur, Helen Pitchik, Vijayaragavan Prabakaran, Mathilda Regan, Katharine Robb, Rucha Shelgikar, and Yu-Cheng Tsai. We thank the members of the WHO Guideline Development Group for their contributions during an early phase of this evidence review. We also acknowledge the support of Bernadette Daelmans, Tarun Dua, and Nigel Rollins at the World Health Organization.
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