Child and adolescent mental health and psychosocial support interventions: An evidence and gap map of low‐ and middle‐income countries

Abstract Background Mental disorders affect about one in seven children and adolescents worldwide. Investment in effective child and adolescent mental health prevention, promotion and care is essential. To date, however, the evidence from this field is yet to be comprehensively collected and mapped. Objectives The objective of this evidence and gap map (EGM) is to provide an overview of the existing evidence on the effectiveness of interventions aimed at promoting mental health and reducing or preventing mental health conditions among children and adolescents in lower‐middle‐income countries (LMICs). Search Methods We searched for studies from a wide range of bibliographic databases, libraries and websites. All searches were conducted in December 2021 and covered the period between 2010 and 2021. Selection Criteria We included evidence on the effectiveness of any Mental Health and Psychosocial Support (MHPSS) interventions targeting children and adolescents from 0 to 19 years of age in LMICs. The map includes systematic reviews and effectiveness studies in the form of randomised control trials and quasi‐experimental studies, and mixed‐methods studies with a focus on intervention effectiveness. Data Collection and Analysis A total of 63,947 records were identified after the search. A total of 19,578 records were removed using machine learning. A total of 7545 records were screened independently and simultaneously by four reviewers based on title and abstract and 2721 full texts were assessed for eligibility. The EGM includes 697 studies and reviews that covered 78 LMICs. Main Results School‐based interventions make up 61% of intervention research on child and adolescent mental health and psychosocial support. Most interventions (59%) focusing on treating mental health conditions rather than preventing them or promoting mental health. Depression (40%, N = 282) was the most frequently researched outcome sub‐domain analysed by studies and reviews, followed by anxiety disorders (32%, N = 225), well‐being (21%, N = 143), and post‐traumatic stress disorder (18%, N = 125). Most included studies and reviews investigated the effectiveness of mental health and psychosocial support interventions in early (75%, N = 525) and late adolescence (64%, N = 448). Conclusions The body of evidence in this area is complex and it is expanding progressively. However, research on child and adolescent MHPSS interventions is more reactive than proactive, with most evidence focusing on addressing mental health conditions that have already arisen rather than preventing them or promoting mental health. Future research should investigate the effectiveness of digital mental health interventions for children and adolescents as well as interventions to address the mental health and psychosocial needs of children in humanitarian settings. Research on early childhood MHPSS interventions is urgently needed. MHPSS research for children and adolescents lacks diversity. Research is also needed to address geographical inequalities at the regional and national level. Important questions also remain on the quality of the available research—is child and adolescent MHPSS intervention research locally relevant, reliable, well‐designed and conducted, accessible and innovative? Planning research collaborations with decision‐makers and involving experts by experience in research is essential.

1 | PLAIN LANGUAGE SUMMARY 1.1 | Evidence and gap map (EGM) finds a stronger focus on treating than preventing mental health problems of children and adolescents Most research on child and adolescent mental health and psychosocial interventions is reactive rather than proactive, with a strong focus on treating rather than preventing mental health problems or promoting mental health.

| What is this EGM about?
Half of all mental health problems originate early in life. Many are preventable, but most remain unrecognised and untreated. Investment in effective child and adolescent mental health prevention, promotion and care is therefore essential.
This EGM provides a visual overview of the existing evidence on the effectiveness of mental health and psychosocial support interventions for children and adolescents aged 0-19 years in lowermiddle-income countries (LMICs).
The interventions are divided into four categories: school-based, community-based, individual and family-based, and digital. These are then further filtered by where, how, for what and to whom they are delivered.

What is the aim of this EGM?
This map visually presents evidence from 697 studies and reviews conducted between 2010 and 2021 on the effectiveness of mental health and psychosocial support interventions for children and adolescents in low-and middle-income countries.

| What studies are included?
A total of 697 studies and reviews are captured in the EGM, focusing on 78 LMICs.

| What are the main findings of this EGM?
Most records cover lower-middle-income countries, with a few covering low-income countries.
Most of the records examine the effectiveness of interventions among adolescents. Most interventions focus on treating mental health problems rather than preventing them or promoting mental health.
School-based interventions are the most studied, followed by community-based interventions, individual and family-based interventions. Digital interventions are the least researched platform.
Most studies investigated mental health conditions, followed by mental health and early childhood development outcomes. Depression was the most frequently researched outcome sub-domain, followed by anxiety disorders, well-being, and post-traumatic stress disorder.

| What do the findings mean?
Research evidence on mental health and psychosocial support interventions for children and adolescents in LMICs is progressively expanding but unevenly distributed among regions and countries and by intervention and outcome domains.
Most of the evidence focuses on treating mental health disorders rather than preventing or enhancing mental health, indicating that current research is more reactive than proactive.
Mental health and psychosocial support research for children and adolescents lacks diversity. It is critical to include certain subpopulations in studies, particularly those that tend to report a higher prevalence of mental health and psychosocial problems and are less likely to have access to mental health care. More evidence is needed on the effectiveness of digital mental health interventions, interventions in humanitarian settings, and interventions for the youngest children.
There are concerns about the quality of the available research.
Progress on mental health and psychosocial support is hampered by a lack of investment in robust research on which interventions work to improve child and adolescent mental health.

| How up-to-date is this EGM?
All the searches were conducted in December 2021, to retrieve all systematic reviews and primary studies published between January 2010 and December 2021, with no language restrictions. 2 | BACKGROUND 2.1 | The problem, condition or issue All children have the right to survive, grow and develop, within the context of physical, emotional and social well-being, to achieve their full potential (UN, 2013). Mental health has been defined as 'a state of well-being in which the individual realises his or her own abilities, can cope with the normal stresses of life, can work productively and fruitfully, and is able to make a contribution to his or her community' (WHO, 2004, p. 11). While this definition moves away from the conceptualisation of mental health as solely the absence of illness, most research and prevalence studies on children and adolescents focus on the mental health conditions that affect mood, thinking and behaviour.
It is estimated that globally mental disorders affect about one in seven children and adolescents aged 10-19 (UNICEF, 2021). The magnitude and nature of child and adolescent mental health conditions can be illustrated through several key figures. First, and despite significant variation, the worldwide pooled prevalence of mental health conditions among children aged 10-19 is estimated at 27.5% for anxiety disorders and 12.7% for depression, which are often comorbid (UNICEF, 2021). Second, depression is among the leading causes of disability among young people while suicide is a leading cause of death among children and adolescents worldwide, ages 10-19 (UNICEF, 2021). Although behavioural problems among younger age groups are prevalent and vary in intensity, there is limited data on global rates and a limited understanding of their longterm consequences (Hong, 2015). Lastly, most mental health conditions originate early in life, with 50% arising before the age of 14 and 75% by the mid-20s (Kessler, 2010;Solmi, 2021). The evidence on effective interventions addressing the mental health and psychosocial well-being of children and adolescents has not been consistently gathered and mapped, despite the prevalence of these conditions. Across the phases of life, experiences and environment present potential risks and opportunities for children and adolescents.
Mounting evidence has shown that the first 1000 days represent a unique opportunity for cognitive growth and early stimulation which are central to healthy mental and emotional lives (Erskine, 2017; Patel, 2018). During the early years of a child's life, parents and caregivers are instrumental in shaping child development and behaviour through adequate child nutrition, education and a nurturing and safe home environment. Middle childhood (5-9 years) are school-going years that provide the context for early peer support and nurturing care through positive interactions as well as providing opportunities for building important life skills (Kieling, 2011).
Adolescence offers a second window of opportunity, representing a critical period in brain development where adolescents adopt and maintaining social and emotional habits and engage in identity formation. This period is characterised by a heightened salience of relationships with peers, as key to shaping and directing young people's psychological development (Mitic, 2021). The onset of puberty at this stage brings unique mental health challenges compounded by physiological and emotional transitions, as well as sexual and risk-taking behaviours. Late adolescence (15-19 years) is shaped by community and social and cultural expectations of acceptable behaviour, gender norms and roles, and the upper end of adolescence comes with pressure to secure employment and gain social and economic independence.
Although most children can adequately recover and adapt using their own resources, childhood and adolescence are also vulnerable periods during which adverse experiences can negatively impact cognitive, emotional, and behavioural development. Without care and support, some children and adolescents can carry the mental and emotional costs YU ET AL. | 3 of 28 of exposure to adverse experiences during earlier years for years to come (Haahr-Pedersen, 2020). Indeed, research shows that in low-resource settings, multiple, overlapping childhood adversities (e.g., violence, neglect, abuse, parental separation or substance use) are consistently associated with poor mental health (Jokinen, 2021;Kieling, 2011;Reed, 2012). At the same time, evidence highlights that adolescence is a time when young people harness skills and traits that can foster resilience, or the learned capacity to deal more effectively with ongoing adversity (Lansford, 2018). Effective positive coping strategies and behaviours adopted and learned during these years can reap benefits into adulthood. Throughout childhood and adolescence, children can be helped to develop resilience by, for example, helping parents to be more responsive to children's emotional and material needs, building community cohesion and providing children with high-quality learning opportunities.
Despite the high burden and early onset, most mental health conditions remain unrecognised and untreated. A global systematic review of survey data in 2004 estimated that 70% of people aged 15 and older who were living with mental health conditions lacked access to adequate care (Kohn, 2004) and that this gap is higher in LMICs, where most (90%) children and young people live (Kieling, 2011). It is important to assess the evidence and treatment gaps in LMICs in more recent years, as this estimate may have changed in the last decade. Additionally, there is growing evidence of effective, affordable and culturally acceptable interventions from high-income settings for preventing and treating mental health conditions that can be implemented in LMICs (Das, 2016). School-based programmes can have significant positive effects on children and adolescents' well-being, including reduced depression and anxiety and improved coping skills (Barry, 2013). Various promotion and prevention approaches have been successfully implemented and rolled-out in community settings (Bradshaw, 2021;Das, 2016;Skeen, 2019). Parent and familyfocused interventions (i.e., psychoeducation, parent and family-skills training, behavioural, psychosocial, and trauma-focused cognitive behavioural therapy) may be beneficial to child and youth mental health and well-being, as well as parenting behaviours and family functioning (Pedersen, 2019).

| Why it is important to develop the EGM
Investment in child and adolescent mental health prevention, promotion and care is essential, but the evidence from this field is yet to be systematically collected and mapped. An EGM generates a clearer picture of the available evidence on interventions to improve child and adolescent mental health in low-resource settings, thereby informing future research, policy and practice.
Promoting, protecting and caring for children and young people's mental health plays a key role in achieving all of the 17 sustainable development goals (SDGs). More specifically, Goal 3 calls on Member States to ensure healthy lives and promote well-being for all at all ages.
SDG target 3.4 aims to reduce premature mortality from noncommunicable diseases and to promote mental health and well-being.
Effective mental health interventions can act as potential development goal accelerators (Sherr, 2020)-with provisions that lead to progress across domains of a child's life and impacting upon multiple SDGs (Patel, 2018). However, mental health care is chronically under-prioritised and under-funded, representing just up to 1% of national health budgets in LMICs (Patel, 2018). In the context of meeting these global goals, there is an urgent need to identify what works in the field of mental health and psychosocial support in low-resource settings and mapping potential areas of investment for future research and programming.
Early evidence from the COVID-19 crisis indicates exacerbated mental health problems during the pandemic, with children and young people globally at risk of psychosocial distress, including anxiety, depression, and externalising behaviours, due to lockdowns, school Against this backdrop, UNICEF has renewed its commitment by setting a new goal to secure investment and action to support and protect the mental health of children and young people. It is estimated that 90% of research on child and adolescent mental health has been conducted in high-income countries and evidence from low-resource settings is sparse (Kieling, 2011). An EGM identifies where the evidence is abundant, but also where limited research and absolute gaps exist and increase the visibility of the available evidence . This resource enables us to identify under-researched areas, countries and population sub-groups and to inform the decisions of international donors, policymakers, practitioners, and researchers as well as UNICEF's research priorities and programmatic actions. A visual representation of the evidence, in the form of a matrix of interventions, allows practitioners, researchers, donors and policymakers to identify and focus on the areas of research that are more likely to inform their work.

| Existing EGMs and/or relevant systematic reviews
A brief desk-based scoping of the literature was conducted to inform the objectives of this EGM, which identified several EGMs covering adjacent topics and themes, and systematic reviews that explore a subset of the interventions and outcomes being proposed for inclusion in this EGM.  (Birnie, 2021). Lastly, an EGM on interventions for children and adolescents with disabilities is currently underway (Thota, 2022) and being conducted under common supervision with this EGM to manage cross-over areas and avoid duplication.
In addition to available and upcoming EGMs, a number of systematic reviews have investigated specific subsets of mental health interventions, outcomes and populations, and will be considered according to our inclusion and exclusion criteria. Barry (2013) (Bangpan, 2017) and Lloyd-Reichling (2005) focused on younger children (0-8 years). Bradshaw (2021) reviewed the evidence on scalable school-based interventions to prevent and address mental health concerns in LMICs. A systematic review identified psychosocial interventions that effectively promote positive mental health and prevent mental health conditions in pregnant and parenting adolescents (Laurenzi, 2020). A meta-analysis identified effective programme components of interventions to promote mental health and prevent mental disorders and risk behaviours during adolescence (Skeen, 2019). In a review of systematic reviews, Das (2016) synthesised the evidence on mental health intervention for adolescents, including but not limited to virtual, individual, group, family and school-based interventions. Another review investigated programmes aimed at promoting mental health and preventing mental disorders and risk behaviours during adolescence (Skeen, 2019).  identified a series of affordable and feasible interventions for children and adolescents in low-resource settings. van Ginneken (2013,2021), respectively analysed the effectiveness of non-specialist and primarly level worker mental health and psychosocial support interventions on child and adolescent mental health.
We also identified and reviewed relevant intervention guidelines and their supporting evidence to define our scope and identify key linkages. The mhGAP (mental health Gap Action Programme) intervention guidelines first developed by WHO in 2010 and updated in 2016 with most recent evidence, provides guidelines for health providers to address mental, neurological and substance abuse disorders (MNS) in non-specialist settings (WHO, 2010). Based on a series of reviews, the Helping Adolescents Thrive (HAT) programme developed guidelines and toolkits for the promotion of positive mental health and prevention of mental health conditions, self-harm, substance use and other high-risk behaviours among adolescents, ages 10-19 (WHO-UNICEF, 2021).
Disease Control Priorities (DCP3), which lays the ground for global priority MNS, includes a chapter on childhood disorders which identifies maternal mental health and parenting skills interventions as holding key potential to the reduction in prevalence of developmental and mental health conditions (Patel, 2016).

| Conceptual framework
The conceptual framework guiding this EGM builds upon the mental health research and evidence generation framework (see This framework incorporates elements of other existing frameworks including: (a) the socio-ecological model (Bronfenbrenner, 1979), which posits that a child's psychosocial well-being depends on a myriad of factors nested within their broader social environment ranging from the household, through to the community and society levels, and the broader socio-cultural and policy environment and can be understood as the different delivery platforms by which interventions are deployed; (b) the social determinants of health approach  which emphasises the role of circumstances in which people are born and grow up, as well as the systems in place to deal with illness; and (c) the life course epidemiology approach (Kuh, 2003) which highlights the factors and experiences over the life course and across generations that impact health outcomes at different ages and life stages.
The EGM utilises this framework by organising interventions according to delivery platforms that correspond to the levels in a child's social ecology. Further, the outcomes will be sensitive to the child's life stage and social determinants of health, thereby including child development outcomes as well. Child and adolescent mental health is complex and changes over time according to individual characteristics, relationships, context and experiences. Therefore, it is hereby understood to encompass both negative and positive mental health outcomes YU ET AL.
| 5 of 28 including well-being and functioning as well as symptoms of distress or sadness and mental health conditions that may require specialised care.
Building on this, we apply the continuum of care model to categorise mental health interventions as prevention, promotion or treatment, as depicted in Figure 2 (Institute of Medicine, 1994). Mental health promotion interventions aim to enhance well-being and create supportive and protective environments for all children and adolescents.
Prevention interventions focus on preventing or reducing the risk of developing a mental health condition by targeting modifiable risk factors and can be universal (delivered to the general population, e.g., primary prevention), selective (population sub-groups deemed to be at risk of mental health conditions developing) or indicated (populations identified at heightened risk for mental health conditions). Treatment interventions are for populations diagnosed with a mental health condition. The framework also includes recovery interventions; however, these will be excluded from the EGM.
F I G U R E 1 Child and adolescent mental health and psychosocial well-being: A conceptual framework for research and evidence generation use. Source:

| OBJECTIVES
The objective of this EGM is to provide an overview of the existing evidence on the effectiveness of interventions aimed at promoting mental health and reducing or preventing mental health conditions among children and adolescents in LMICs.
Consistent with this, the EGM will: 1. Identify, describe and visually represent the existing evidence from systematic reviews and primary studies on the effectiveness of mental health interventions for children and adolescents.
2. Identify existing gaps in evidence to better inform practice and future primary research.
3. Identify clusters of primary studies that offer opportunities for evidence synthesis.

| EGM: Definitions
In contrast to systematic reviews, EGMs do not aim to synthesise the outcomes or key messages from available evidence, but instead aim to map the availability of evidence, coverage and gaps across the various dimensions of the EGM framework and make the evidence discoverable, accessible and usable. EGMs provide an overview of the existing evidence on a topic, theme or sector to signpost where evidence exists and/or where it is lacking (Bakrania, 2020). The method for this EGM is based on an a priori protocol . We mapped evidence on the effectiveness of child and adolescent (ages 0-19) Mental health and psychosocial support (MHPSS) interventions in LMICs within the last 12 years. A description of these criteria is provided below, and an overview of search methods and sources used is presented in Supporting Information: Appendix 2.

| Types of populations
Children and adolescents are defined as any person from 0 to 19 years of age and classified according to UNICEF's age criteria stated as follows: early childhood (0-4 years), middle childhood (5-9 years), early adolescence (10-14 years) and late adolescence (15-19 years).
Primary studies where less than 50% of the sample fall within the 0-19 age range or that do not provide sufficient information of age composition will be excluded.

Population subgroups of interest includes children in alterna-
tive care, children with disabilities, LGBTQIA+ children, ethnic or racial minorities, child workers, married children, street children, children with chronic health conditions, pregnant adolescents and adolescent parents and forcibly displaced children. We also note whether studies or reviews focus on girls/females, boys/males and/or other.
LMIC are defined according to the World Bank's regional classification by country gross national income as: low-income, lower middleincome, upper middle-income economies (The World Bank, 2021).

| Types of interventions
MHPSS is defined as 'any type of local or outside support that aims to protect or promote psychosocial well-being and/or prevent or treat

| Types of outcome measures
The main outcome categories are listed in Table 2. Systematic reviews and primary studies investigating the impact of MHPSS interventions on violence prevention outcomes (addressed in the violence against children EGM; Pundir, 2020) were excluded.
We used the International Classification of Disease (ICD-11) criteria for including mental health conditions. The terms 'internalising' and 'externalising' refer to internally and externally focused symptoms of mental health conditions, respectively. These wellestablished and widely used groupings are derived from factor analyses of psychological problems identified by clinically referred children and describe behavioural, emotional and social problems. we have also included 'other' categories for relevant outcomes that may emerge from the included studies and relate directly to the outcomes described above (e.g., sadness or hopelessness as outcomes related to depression, or self-efficacy and prosocial behaviours as outcomes related to mental well-being). To capture key early childhood indicators, we looked at child development outcomes such as social-emotional learning and cognitive development. These are critical processes through which children acquire and apply knowledge and skills to cope with challenges, manage interpersonal relationships and emotions, solve problems and make informed decisions. These indicators are also linked to later-life mental health outcomes (Black, 2017;Patel, 2018).

| Types of study designs
The study designs included in the EGM are systematic reviews and effectiveness studies in the form of randomised control trials and quasiexperimental studies. We used White (2014) Table 3 presents the filters of the EGM.

| Planned analysis
The EGM report provides tabulations and/or graphs of the number of studies, with accompanying narrative description, by: • Intervention category and subcategory Also, more than one outcome domain and subdomain can be measured in one primary study or systematic review. Various records are counted more than once, which is necessary to provide an overview of the EGM's results. conducted in a humanitarian or conflict-affected region. • COVID-19: Study or review explicitly mentions having been conducted in the context of the COVID-19 pandemic or including studies conducted in the context of the COVID-19 pandemic. • Physical activity: study or review includes physical activity interventions-physical activity is 'any body movement that is produced by the contraction of skeletal muscles that increase energy expenditure' whereas exercise is 'a subset of physical activity that is planned, structured and deliberate'. • Format: Individual, dyad and group-based interventions Population • Age group: early childhood (0-4); middle childhood (5-9); early adolescence ( Among all records of studies and reviews, we identified 24 (3%) protocols of systematic reviews and primary randomised controlled trial studies (see list of ongoing studies and reviews in 'References').
Due to the large number of studies screened at full text, we do not provide a full list of excluded studies, but the list is available upon request.

Interventions
Most research of mental health and psychosocial support interventions (61%, N = 425) conducted in LMICs, regardless of whether they focus on promotion, prevention or treatment, has been conducted in school settings (see Table 4). For instance, El-Khodary and Samara   well-being of 180 Thai adolescents. Four percent of records (N = 26), which are all systematic reviews, researched all three formats. Eight percent of studies and reviews (N = 53) did not report the format of provision.
A total of 82 studies and reviews included interventions consisting of physical activities. Most of them were designed in school-based settings (N = 66) and for treatment (N = 51). For example, Cocca and colleagues (2020) measured psychological well-being, self-esteem, stress, and anxiety among 252 Mexican schoolchildren ages 10-12 before and after they attended a 6-month game-based physical education programme at school.
This type of interventions was more frequently delivered to early (N = 67) and late adolescents (N = 55) than early (N = 11) and middle childhood (N = 45) and most were delivered in groups (N = 69).
As presented in Table 5 All five sub-domains in early childhood development outcomes were covered by less than 10% of studies and reviews. Within mental health outcomes, two of six sub-domains were measured by less than 10% of studies and reviews, which were ability to cope or social connectedness. Five sub-domains in mental health conditions outcomes-eating disorders, oppositional defiant disorder, suicidal and self-harm behaviour, conduct disorder, and alcohol and substance abuse are also covered by less than 10% of studies and reviews. F I G U R E 3 Intervention platform by intervention type.

Age groups
Most included studies and reviews investigated the effectiveness of mental health and psychosocial support interventions in early (75%, N = 525) and late adolescence (64%, N = 448), followed by 45% (N = 317) of studies and reviews which investigated middle childhood, and 22% (N = 150) on early childhood ( Figure 6). Most studies looked into treatment interventions across all age groups with the exception T A B L E 5 Studies and reviews by outcome domains and sub-domains.  There are 58 studies (57%) focusing on group-based interventions in school settings with a sample size larger than 300.
As presented in Figure 10, among all reviews except protocols (N = 216), 46% of reviews (N = 100) contain equal or fewer than 20 primary studies. Only less than one quarter of reviews (24%, N = 51) have equal to or more than 40 primary studies.

Settings
This map covered 78 of 138 LMICs (57%), including 12 low-income countries (44% of all low-income countries), 31 lower-middle-income countries (56% of all lower-middle-income countries) and F I G U R E 6 Distribution of studies and reviews by age.
F I G U R E 7 Distribution of studies and reviews by intervention type and age. YU ET AL.
| 15 of 28 F I G U R E 8 Number of studies and reviews by sub-groups.
F I G U R E 9 Number of studies by sample size.
F I G U R E 10 Number of reviews by included primary studies.
35 upper-middle-income countries (64% of all upper-middle-income countries). Various studies (mostly systematic reviews) covered both high-income countries and LMICs and were classified as global (31%, N = 219). We coded the country of a study or review according to the country in which the research was conducted. A study or review may be coded for more than one country.
The top 10 LMICs that were covered by most studies and reviews were presented in Figure 11. Most studies and reviews were conducted in Iran (21%, N = 146), followed by China (16%, N = 113) and India (12%, N = 81).
With an average of 58 studies and reviews published yearly, showcasing data from LMICs, Figure 12 indicates the field of child and adolescent mental health has been expanding progressively during the last 12 years with a 16% average year-on-year increase rate, and a 41% compound annual growth rate in the number of publications. F I G U R E 13 Geographic distribution of studies. All HICs are not labelled in any colour in this map as they are out of the scope. Any LMIC in grey colour means no study or review were conducted in this country. The designations employed in this publication and the presentation of the material do not imply on the part of UNICEF the expression of any opinion whatsoever concerning the legal status of any country or territory, or of its authorities or the delimitations of its frontiers.

Study designs
Most records were quasi-experimental studies (44%, N = 307), followed by systematic reviews including protocols (34%, N = 239) and randomised controlled trials including protocols (20%, N = 140). As presented in Figure 15, school-based interventions are the most common intervention platform covered across these three publication types, followed by community-based intervention as the second and individual and family-based interventions as the third.

| DISCUSSION
Child and adolescent mental health in low-resource settings is inadequately understood and developed as a field (Kumar, 2021). Regardless of the type of intervention (i.e., prevention, promotion, or treatment), most mental health research is conducted at educational settings and focuses on early and late adolescence.
Schools are one of the most convenient locations (i.e., feasibility and cost-effectiveness) for reaching a wide number of children and adolescents and their families (Barry, 2013). Evidence from systematic reviews suggests that mental health programmes incorporating life skills, social and emotional learning to address emotional and behavioural problems can improve for children's emotional and social functioning, including reduced depression and anxiety and improved coping skills (Barry, 2013). Although future systematic reviews are needed, considering that nearly 100% of published studies in psychology confirm their initial hypothesis (Haeffel, 2022), there is likely evidence supporting the use of MHPSS interventions in school settings. Despite the potential for early intervention in educational settings, a recent review of the effectiveness of universal school-based mental health interventions highlights the lack of evidence supporting the use of preventive interventions (Bradshaw, 2021  A recent systematic review of the effects of early parenting interventions on early childhood development outcomes conducted in LMICs found that although trials supported benefits on a wide range of outcomes, they also revealed fading effects over time and inconclusive findings on long-term impacts (Jeong 2021 In this EGM, we found a large proportion of studies and reviews focused on treatment interventions in comparison to prevention and promotion interventions. It is important to note, however, that these boundaries are sometimes difficult to draw (Purgato, 2020). This EGM excluded large population-level programmes such as mental health policies and legal frameworks. Considering the potential of appropriately formulated and implemented policies to improve child and adolescent mental health and that many countries do not possess any policies on mental health (Zhou, 2018), this remains an important area for future research. This EGM focused on the effectiveness of MHPSS interventions on mental health and psychosocial outcomes.
However, MHPSS interventions have intended and unintended impact on social outcomes (e.g., strengths of relations within communities, discrimination, violence) and the research is needed within this area (Ubels, 2022). Lastly, due to the large number of studies and reviews identified in this EGM, we did not extract other important criteria such as whether studies measured long-term effects of interventions or information on who provided the intervention. We encourage reviewers exploring effectiveness findings of these interventions to extract and report on findings of these criteria.

| Differences from the protocol
After the publication of the protocol , we revised the resources and added several websites and grey literature sources to our list and removed a few sources. We removed PROSPERO, ClinicalTrials.gov and WHO ICTRP because we had limited time and human resources to contact the authors of ongoing studies for data or publications, these were not providing unique results, and their data were not peer-reviewed. We removed the Bing search engine because Google already retrieved the test relevant results and considered to be enough. We could not access WHO's Global Health Library; however, we searched Global Index Medicus which is a similar source to WHO's Global Health Library. Although we were able to run all the intended searches in Google Scholar, this source blocked our attempts to export the search results for all the following search strategies. We believe the extent to which we may have missed studies due to this was minimal as we conducted other extensive searches in main databases. We also added CENTRAL to the list of sources as suggested by the peer-reviewer of the protocol and added HMIC Health Management Information Consortium as a relevant source that was not listed in the protocol. to mental health disorders (Patel, 2018). Funding for mental health research has been found to be too inequitable, with less than 10% of funding being spent in countries that have 90% of global health problems and too skewed, with more than 50% devoted to biological research and just about 7% allocated to health services research, clinical and prevention research, respectively (Patel, 2018).
While new donors are emerging and the COVID-19 pandemic is driving a small uplift in mental health investments for the general population, the limited investment that is allocated for children's, adolescents' and young people's mental health, often only addresses surface-level factors through reactive interventions rather than proactive programmes. This delivers short-term wins instead of long-term change or does not become available until young people have reached a point of crisis. This EGM assists MHPSS practitioners advocate, fund and make child and adolescent MHPSS a global priority.

DECLARATIONS OF INTEREST
None known.

Plans for updating the EGM
Once completed, the EGM will be updated yearly, depending on the need of an update (availability of new reviews and primary studies).
Regular updates are also subject to availability of funding. If funding is available, UNICEF Innocenti-Global Office of Research and Foresight takes responsibility for updating the review.

SOURCES OF SUPPORT
Internal sources • UNICEF Innocenti-Global Office of Research and Foresight, Italy The funding for this EGM is provided by UNICEF Innocenti-

DAS 2016
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