The Impact of the COVID-19 Pandemic and Societal Infection Control Measures on Children and Adolescents' Mental Health: A Scoping Review

Background: The COVID-19 pandemic is primarily a crisis that affects people's physical health. However, it is well-known from previous epidemics and pandemics that there are other indirect negative impacts on mental health, among others. The purpose of this scoping review was to explore and summarise primary empirical research evidence on how the COVID-19 pandemic and societal infection control measures have impacted children and adolescents' mental health. Methods: A literature search was conducted in five scientific databases: PubMed, APA PsycINFO, Web of Science, CINHAL, and Social Science Premium Collection. The search string was designed using the Population (0–18 years), Exposure (COVID-19), Outcomes (mental health) framework. Mental health was defined broadly, covering mental well-being to mental disorders and psychiatric conditions. Results: Fifty-nine studies were included in the scoping review. Of these, 44 were cross-sectional and 15 were longitudinal studies. Most studies reported negative impact of the COVID-19 pandemic on child and adolescent mental health outcomes, yet the evidence was mixed. This was also the case for studies investigating societal control measures. Strong resilience, positive emotion regulation, physical activity, parental self-efficacy, family functioning and emotional regulation, and social support were reported as protective factors. On the contrary, emotional reactivity and experiential avoidance, exposure to excessive information, COVID-19 school concerns, presence of COVID-19 cases in the community, parental mental health problems, and high internet, social media and video game use were all identified as potentially harmful factors. Conclusions: Due to the methodological heterogeneity of the studies and geographical variation, it is challenging to draw definitive conclusions about the real impact of the COVID-19 pandemic on the mental health of children and adolescents. However, the existing body of research gives some insight to how parents, clinicians and policy makers can take action to mitigate the effects of COVID-19 and control measures. Interventions to promote physical activity and reduce screen time among children and adolescents are recommended, as well as parenting support programs.


INTRODUCTION
The outbreak of a new respiratory syndrome, declared as coronavirus disease 2019 (COVID- 19), was first identified in Wuhan, China, in December 2019 (1) and continued to spread rapidly around the world. On March 11th 2020, the World Health Organisation (WHO) declared COVID-19 as a global pandemic that had spread to 114 countries. COVID-19 showed a high transmission ability compared with SARS (severe acute respiratory syndrome) and MERS (Middle East respiratory syndrome); however, on the other hand, COVID-19 showed a lower mortality rate (4.5-6.0%) when compared to SARS (9.6%), and MERS (34.4%) (1).
It is believed the virus that causes COVID-19 spreads mainly from person to person. As an attempt to slow down the spread of the virus, in mid-March 2020, many countries took preventive measures such as social distancing and quarantine. By September-October 2020, after a relaxation of lockdowns and the population's precautionary behaviours, indicators of a second wave were emerging in many European countries. From December 2020, international vaccination roll-out programmes commenced. Now more recently, in February-March 2021, there are concerns regarding a third wave. Restrictions are coming back but, in some countries, not as strict as in the first wave. By end of March 2021, more than 2.8 million people in the world had died from the virus and nearly 130 million had reported infection.
The COVID-19 pandemic is primarily a crisis that affects people's physical health, but it is well-known from previous epidemics and pandemics that the event, including societal measures to control infection, also affects the mental health of the population directly and indirectly (2), among a number of other potential negative outcomes. The societal infection control measures have proved to be successful controlling the spread of the virus (3); however, at the same time, the interruption of the daily routine of children, adolescents and their families has impacted their lives (4).
COVID-19 is an unprecedented global crisis compared to the most recent epidemics and children and adolescents are experiencing a prolonged state of physical isolation from their peers, teachers, extended families, and community networks (5). Added to children and adolescents' fear of personal and family member infection, there are other pandemic-related factors that could affect mental health outcomes such as family job or financial loss and social isolation due to infection containment measures (5).
It is crucial to understand and investigate the real impact of the COVID-19 pandemic and related societal measures to develop, adapt, and implement mitigation strategies for these outcomes in order to help children and adolescents' mental health and well-being during these stressful times as well as for future similar pandemics.
The aim of this scoping review was to explore and summarise primary research evidence on how the COVID-19 pandemic and societal infection control measures (such as "lockdown, " quarantine, social isolation, social distancing, and school closures) aimed at minimising the spread of the disease have impacted children and adolescents' mental health, from birth up to 18 years.

METHODS
The scoping review followed the methodological framework as described by Arksey and O'Malley (6). The framework sets out five steps: (i) identifying the research question(s); (ii) identifying relevant studies; (iii) study selection; (iv) charting the data; and (v) collating, summarising and reporting the results. Yet, Arksey and O'Malley state that researchers should engage with each stage in a reflexive way (6). In other words, the process should not be considered linear but iterative. This means steps can be revisited, if needed.

Identifying the Research Questions
In order to thematically construct the account of existing literature, specific research questions were developed through discussion among the authors: 1. Has the COVID-19 pandemic and societal infection control measures impacted child and adolescent mental health? 2. What is the evidence from different geographical regions? 3. Are there any protective factors associated with a lower likelihood of mental health problem outcomes? 4. Are there any factors associated with a higher likelihood of mental health problem outcomes? Empirical study with primary data and quantitative analysis Qualitative studies Books, book chapters, editorials, opinion pieces, indices, research letters, conference reports and posters, case-reports, case-series, pre-print, letter to the editor, commentary, and pilot studies Systematic reviews, scoping reviews, narrative reviews rapid reviews, and other reviews

Collating, Summarising, and Reporting the Results
As scoping reviews seek to present an overview of all material reviewed (6), tables were constructed of all cross-sectional studies ( Table 2) and all longitudinal studies ( Table 3) included in the review. The reason for highlighting the methodological difference between studies was 2-fold. First, it is a logical and informative way to organise the studies when reporting the overall field of research. Second, it was used as a prioritisation strategy for the review update, as longitudinal studies are more likely to indicate causality, which is important when issuing recommendations based on the data. Within each table, the studies were organised by continent and country.

RESULTS
The first search yielded 2,452 non-duplicate references and resulted in 49 eligible studies (longitudinal and cross sectional) while the second search, used to update the review, yielded 3,309 non-duplicate references and resulted in 10 eligible studies (longitudinal only) (Figure 1). Some included studies had multiple aims, not all of which were related to a mental health outcome; only findings related to mental health outcomes were reported in this review.
Has the COVID-19 Pandemic and Societal Infection Control Measures Impacted Child and Adolescent Mental Health?

COVID-19 cases in community Depression
The presence of COVID-19 cases in communities contributed to adolescents' poorer mental health, and the association was stronger for older adolescents.

Anxiety and depression
The prevalence of depressive symptoms, anxiety symptoms, and a combination of depressive and anxiety symptoms was 44, 37, and 31%, respectively. There was a high prevalence of psychological health problems among adolescents, which was negatively associated with the level of knowledge about and the prevention and control measures for COVID-19

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Frontiers in Psychiatry | www.frontiersin.org Moderate depressive symptoms were found in 9% of junior school and 7% of high school students, and severe to extremely severe depressive symptoms were found in 5% of junior school and 3% of high school students. Moderate anxiety symptoms were found in 10% of junior school and 11% of high school students, and severe to extremely severe anxiety symptoms were found in 10% of junior school and 7% of high school students. Moderate stress symptoms were found in 6% of junior high school students and 7% of high school students, and severe to extremely severe stress symptoms were found in 3% of junior school and 3% of high school students. Trauma-related distress was found in 21% of junior school and 23% of high school students, with no significant between-group differences. Zhang et al. (20)

COVID-19 pandemic
Quality of life Self-reported quality of life scores of children were generally good. The highest average score was for "physical well-being" and "family," while the lowest average score was for "friends" and for "self-esteem." Kilinçel et al. (28). https:// doi.org/10.1111/appy. 12406 Turkey, Asia/Europe "To determine the results of home-quarantine measures taken for adolescents during the pandemic and the factors affecting these results."

Loneliness and anxiety
The closure of schools and home-quarantine increased levels of anxiety and loneliness. Exposure to excessive information caused elevated levels of stress and anxiety among children.
Seçer and Ulaş (29). https://doi.org/10.1007/ s11469-020-00322-z Turkey, Asia/Europe "To examine the mediating role of emotional reactivity, depression anxiety and experiential avoidance in the relationship between the fear of COVID-19 and obsessive compulsive disorder (OCD) symptoms in adolescents." Fear of COVID-19 OCD, emotional reactivity, avoidance, depression, and anxiety The effect of COVID-19 fear on OCD is mediated by emotional reactivity, experiential avoidance and depression-anxiety Frontiers in Psychiatry | www.frontiersin.org Anxious participants indicated they used social media more often to actively seek for a manner to adapt to the current situation, and to a lesser extent as a way to keep in touch with friends and family. Participants who were feeling lonely were more inclined to use social media to cope with lacking social contact.  Closure of schools and social isolation were the two main problems students say they face. Whilst the majority (68%) were "happy," 16% of students had mental health scores that indicate major depression.
Frontiers in Psychiatry | www.frontiersin.org 35% of adolescents reported a significant increase in psychological stress. Adolescents and parents who experienced a significant increase in psychological stress had lower baseline stress levels than those who did not experience increased psychological stress during COVID-19 lockdown. Significant adolescent risk factors for increased psychological stress included financial worries, increased psychological stress of the corresponding parent, procrastination, limited access to emotion regulation strategies and mainly staying at home during COVID-19 lockdown. High emotional awareness served as a protective factor for adolescents.

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Frontiers in Psychiatry | www.frontiersin.org 21% of the children indicated that stress applied to them in the last 2 weeks of the COVID-19 lockdown. Children's externalising behaviour during the lockdown was significantly predicted by prior externalising behaviour. Children with higher levels of externalising behaviour prior to the lockdown perceived more stress during the lockdown, resulting in an increase in externalising behaviour during the lockdown. Perceived stress of children and parents were not significantly correlated. Parental over-reactivity was significantly related to children's perceived stress.

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Frontiers in Psychiatry | www.frontiersin.org Psychiatric symptoms increased during the pandemic, including depression, panic/somatic symptoms, generalised anxiety, and social anxiety. Post-hoc analyses reveal that depression and panic/somatic symptoms increased for females. In female participants, there was a nearly 3-fold increase in rates of clinically elevated depression from before to during the pandemic and nearly half (49%) experienced clinically elevated generalised anxiety during the pandemic. Greater COVID-19 school concerns were associated with increased depression symptoms and greater COVID-19 home confinement concerns were associated with increased generalised anxiety symptoms, and decreased social anxiety symptoms. None of the composites were associated with panic/somatic symptoms. Gender did not moderate any relationship between pandemic experiences and change in CDI or SCARED symptoms.

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Frontiers in Psychiatry | www.frontiersin.org The majority of youths reported only "a little" or "not at all" for difficult family relationships, loneliness, stress, parent stress, conflict with parents, worsened relationships with parents, and parent impatience during the pandemic. Around 80% of students reported "a little," "a lot," or "a whole lot" for parents' level of understanding, ability to make the child feel better, and ability to help the child manage stress during the pandemic. For youths who had elevated levels of mental health problems before the pandemic, symptoms were significantly reduced across domains during the pandemic. Reductions in internalising, externalising, and total problems were clinically significant. For other youths, there were statistically significant reductions in internalising and total problems, and no change in attention or externalising problems. Post hoc analyses revealed that better family functioning was consistently related to lower mental health symptoms in youths during COVID-19 follow-ups. In general adolescents reported low levels of mental health problems before the COVID-19 pandemic. Small significant increases in depressive symptoms, anxiety symptoms and loneliness were detected between before and during the pandemic. Adolescents reportedly spent less time with friends and, despite online interaction, felt a lack of emotional connexion and a decrease in overall friend support. On the contrary, adolescents perceived overall increases in family support and some adolescents perceived decreases in family conflict during COVID-19. The decline in friend support during the pandemic was found to be related to higher depressive symptoms, and the feeling of more conflict with friends during the pandemic was also found to be related to more loneliness. Additionally, greater perceived increases in family conflict during the pandemic was found to be related to more depressive symptoms and greater loneliness.

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Frontiers in Psychiatry | www.frontiersin.org In general, adolescents reported low to moderate levels of COVID-19 related stress. The most distressing issue reported was not being able to see friends, closely followed by a friend or family member contracting and getting very sick and/or dying from COVID-19. Significant increases in depression and anxiety symptoms were reported as well as a significant decrease in life satisfaction from before to during the pandemic, which was particularly pronounced among girls. Age did not moderate change in depressive symptoms, anxiety, or life satisfaction. COVID-19 related stress, online learning difficulties, and increased conflict with parents predicted increases in mental health problems from before to during the pandemic, whereas adherence to stay-at-home orders (government restrictions) and feeling socially connected (greater exposure to traditional media) during the COVID-19 lockdown was associated to less distress. (54, 65), and life satisfaction (64). However, a study from Spain reported no significant change among preschool-aged children and, despite some statistically significant differences in a primary school-aged group, no change was identified for depression or challenging behaviour (55). Similarly, a study from China reported significant changes in anxiety among adolescents but not children, and no change was identified for depression (67). In a Canadian study, significant impact on emotional and behavioural problems was detected for male children enrolled in early childhood education, but not females (59). A study from Australia reported no differences in adolescents' reports on negative affect, nor positive affect, during the pandemic as compared to a baseline period (57).
Longitudinal research from the Netherlands reported findings with a developmental perspective; although a slight reduction was seen in externalising problems from pre-pandemic to during pandemic, this was considered in line with developmental trajectory and it was interpreted that the pandemic had decelerated the expected reduction (56). A further study, which used a majority Hispanic/Latinx sample in the United States (US), reported a reduction in emotional and behavioural problems from before to during the pandemic; the reduction was greater for those who had elevated mental health problems pre-pandemic (62). One of the identified longitudinal studies did not seek to compare pre-and post-pandemic mental health outcomes but instead to track the trajectory of mental health symptomatology during the pandemic period among youth in New York, US (68). This study reported that symptoms of depression and anxiety peaked around late April/early May and then decreased through May to July 2020 (68).
When specifically considering the impact of societal control measures, which have varied internationally, many studies suggested negative impact yet the evidence was mixed. The closure of schools and home quarantine, sometimes referred to as "lockdown, " was reportedly negatively associated with children's mental health outcomes across various international settings (28,33,39,53,54,56,66), as were physical distancing measures (65). Boredom and difficulty concentrating emerged as specific concerns (35,38), which is understandable given the loss of routine that comes with such control measures. In a couple of studies, the children themselves reported the closure of schools, social isolation and not being able to see friends as the most pressing problems they were facing during the pandemic (50,64), and a further study reported that decline in support from friends was associated with higher depressive symptoms (63). Yet, other studies reported a lack of association between degree of social distancing engagement (46) and isolation (30) with mental health outcomes, and one study even detected an association between adherence to stay-at-home orders and lower levels of distress (64). Interestingly, one study indicated that greater COVID-19 home confinement concerns were associated with increased generalised anxiety symptoms, yet decreased social anxiety symptoms (60). There was also indication of the societal control measures enhancing family togetherness (33,38,63), and in one study around a fifth of the children reported being more satisfied with life during school closures (15).

What Is the Evidence From Different Geographical Regions?
Nearly half of the included studies were conducted in Asia (n = 25), predominantly in China (n = 17/25). As COVID-19 originated in China, it is not surprising that the country is at the forefront of publishing research about the pandemic; yet, it must be recognised that many factors affect investigation time frames. The Chinese government imposed strict containment measures in January 2020, which were eased from February 2020 with localised restrictions re-imposed in new "hotspots." The number of reported COVID-19 cases has remained low ever since. Although relatively brief, the societal infection control measures in China were among the strictest worldwide. Theoretically, it could be argued that such strict measures had a particularly adverse effect on children and adolescents' mental health. Most of the Chinese research was cross-sectional (n = 15/17), and largely explored depression and/or anxiety symptomatology among children and adolescents (n = 10/15), with prevalence rates ranging from 2 to 44%. Despite the mixed cross-sectional evidence, the two longitudinal studies conducted in China (51,67) reported increased psychological distress, particularly anxiety symptoms among adolescents.
Further research from Asia was conducted in Bangladesh (n = 1), Iran (n = 2), Israel (n = 1), Taiwan (n = 1), and Turkey (n = 3). All of these studies were cross-sectional. Although some studies only reported prevalence of mental health symptomatology (23) and perceived quality of life (27), others explored mediating factors and indicated evidence of interaction between internet-related behaviours and child and adolescent mental health (24,26), as well as parental mental health and child and adolescent mental health (7,25).
Only one included study was from Africa, which was conducted in Nigeria where a nationwide lockdown was introduced in late March 2020 and lifted in May 2020 due to public unrest about the socio-economic consequences. This single study explored the impact of isolation on school students (30); it reported no impact on COVID-19 anxiety and lower examination anxiety among an isolated group compared with a non-isolated group. Since the publication of the study, Nigeria has experienced an increase in COVID-19 cases and imposed further societal lockdown measures.
Of the European studies (n = 16), half were conducted in Italy (n = 8). In February 2020, there was a severe outbreak of COVID-19 in northern Italy, which was placed into lockdown. A national lockdown followed in March 2020, which was gradually eased from May 2020. During the first wave of the pandemic, the number of active cases in Italy was one of the highest in the world. Most of the Italian studies were crosssectional (n = 7) and reported high levels of mental health and well-being issues among children and adolescents during the pandemic, as well as evidence of interaction between parental mental health and child and adolescent mental health (36,37). The only longitudinal study conducted in Italy reported that, compared with 1 year earlier, adolescents experienced fewer positive emotions and more negative emotions after the COVID-19 national lockdown (54).
Further research from Europe was conducted in Belgium (n = 1), Spain (n = 4), Germany (n = 1), the Netherlands (n = 2), and the United Kingdom (n = 1). Increased depressive symptoms were reported in the UK (66), there was some evidence of increased psychological stress in Germany (53), the evidence from Spain was mixed (38)(39)(40)55), and only slight impact was interpreted in the Netherlands (56,57). The Belgian study explored the relationship between anxiety and social media (31). All these European countries have implemented a "lockdown" of some form. Yet, the lockdown approach in the Netherlands has been relatively relaxed compared to other European countries, with the government implementing its so-called "intelligent lockdown" whereby people were asked to stay home but were still allowed to move around freely as long as they kept a distance of 1.5 m to others. The varying "lockdown" approaches could, in part, account for the varying impacts on child and adolescent mental health; yet, it is difficult to conclude this from the available evidence.
There were 13 studies from North America and most of the studies (n = 10/13) were conducted in the US and the remaining (n = 3/13) in Canada. The majority of the US studies were crosssectional (n = 6/10) and reported: negative association between the pandemic and societal control measures and the mental health of children and adolescents (43,47); how parental mental health was associated to their children/adolescents' mental health (43,48) or how parents' and children's well-being in the postcrisis period was strongly associated with the number of crisisrelated hardships (such as job loss, income loss, caregiving burden, and illness) that the family experienced (45). One study reported that children's mental health fell within the clinical range, however, mental health symptoms were positively associated with the number of children in the home (44). Oosterhoff et al. (46) did not find any evidence of a potential association between degree of social distancing nor any indicator of mental health. Three of the longitudinal studies reported a significant increase, albeit small, in symptoms of mental illhealth during the pandemic (compared to before the pandemic) (60,63,68).
The two Canadian cross-sectional studies reported: 43% of adolescents expressed they were "very concerned" about the pandemic (42) while Carroll et al. (41) reported that, according to parents, almost half (49%) of children had very little concern about COVID-19, 38% were somewhat concerned, and 7% were very much concerned. Browne et al. (59), the only longitudinal study from Canada, reported that male children's mental health problems worsened significantly during the pandemic. No significant differences over time were observed for females. There were two cross-sectional studies conducted in South America as another geographical region: one from Brazil and the other from Ecuador. Garcia de Avila (49) assessed the prevalence of anxiety among Brazilian school-children and reported a high prevalence of anxiety (19%), especially among children with parents with essential jobs and those who were social distancing without parents. Asanov et al. (50) assessed the mental health of Ecuadorian high-school students during the COVID-19 quarantine and reported that 16% of students had mental health scores that indicated major depression.
The two studies conducted in Australia were both longitudinal studies and reported the negative impact of COVID-19 and associated societal control measures on the mental health of children and adolescents. Magson et al. (64) found significant increases in depression and anxiety symptoms as well as a significant decrease in life satisfaction among adolescents, from before to during the pandemic, which was particularly pronounced among girls. Similarly, Munasinghe et al. (65) investigated changes in well-being during the early period of physical distancing among adolescents and results highlighted that the implementation of physical distancing interventions was associated with decreases in well-being.
Are There Any Protective Factors Associated With a Lower Likelihood of Mental Health Problem Outcomes? Some potential protective factors, i.e., characteristics associated with a lower likelihood of negative outcomes or that reduce the negative impact, were identified in the scoping review. With regard to internal protective factors, strong resilience and positive emotion regulation were associated with better mental health outcomes among adolescents (17,20,53). On a behavioural level, physical activity was reportedly associated with improved mood among children and adolescents (11,21). The social environment also appears to play a role, with parental self-efficacy (36), family functioning (62), and emotion regulation (25) as well as level of social support (12) associated with better outcomes.

Are There Any Factors Associated With a Higher Likelihood of Mental Health Problem Outcomes?
A number of factors associated with poorer mental health outcomes were identified in the scoping review. The level of concern about COVID-19 among adolescents was found to be associated with poorer mental health outcomes (29,42), and could be related to internal factors such as emotional reactivity and experiential avoidance (29,53) as well as exposure to excessive information (28). Similarly, greater COVID-19 school concerns were associated with increased depression symptoms (60). The presence of COVID-19 cases in adolescents' communities contributed to poorer mental health, which was more pronounced for older adolescents (13). Several studies indicated that parental mental health problems were related to poorer child and adolescent outcomes (7,16,25,37,48,53,56), which strengthens the evidence that social environment is an important factor. Internet, social media and video game use was another common research topic, evidence from which suggests negative association with child and adolescent mental health (9,18,24,26,31,51,67).

DISCUSSION
This scoping review brings together all the published studies exploring child and adolescent mental health during the COVID-19 pandemic around the world, published until December 2020, and all longitudinal studies until early May 2021. In just over a year there were 59 studies that met the inclusion criteria for this review. The figure would have been higher if the focus of the second review process had not been narrowed to longitudinal studies only. This highlights the extensive research activity during the pandemic period. Yet, only 15 of the studies adopted a longitudinal research design, which means evidence on how the COVID-19 pandemic and societal control measures have affected the mental health of children and adolescents is still somewhat limited. The definition of "child" and "adolescent" varied across the included studies; yet, most reportedly involved adolescents (n = 30; 63%). Around a third of the studies relied only on parent reports to measure child and adolescent mental health (n = 19: 32%). Across all the included studies, a range of outcome measures were used to assess mental health including bespoke questions formulated for the purpose of the research (Tables 2,  3). It is important to highlight here the timing of when data was collected and how it changed from one study to the other: in some of the studies, data were collected at the very beginning of the pandemic (already from February 2020); some other studies collected their data during the first COVID-19 peak (March, April, or May 2020) according to each country; and in some other studies data were collected when the pandemic seemed to be under control and societal control measures were no longer very strict. There is some evidence to suggest that the timing of data collection could affect findings (68).
Most studies reported negative impact of COVID-19 on child and adolescent mental health outcomes, yet the evidence was mixed (Tables 2, 3). This was also the case for studies investigating societal control measures. Strong resilience, positive emotion regulation, physical activity, parental self-efficacy, family functioning and emotional regulation, and social support were reported as protective factors. On the contrary, emotional reactivity and experiential avoidance, exposure to excessive information, COVID-19 school concerns, presence of COVID-19 cases in the community, parental mental health problems, and high internet, social media, and video game use were all identified as potentially harmful factors.
Collating the evidence in a scoping review such as this provides an initial step toward addressing negative impact of the pandemic and child and adolescent mental health. By taking the various findings across the body of research into consideration, interventional strategies can be developed. Taking action now could mitigate longer term impact on the overall health and mental health of children and adolescents. Not only could this be helpful in the present day, but it could also be informative for future pandemics. In terms of the nature of intervention, the aforementioned protective and harmful factors identified in the literature provide grounding for potential intervention targets.
Under this unprecedented and current situation due to the COVID-19 pandemic and societal infection control measures, the levels of physical activity and sedentary behaviour of children and adolescents are important aspects to be considered. Physical activity was shown to be associated with better mood state during the pandemic by two studies (11,21). Both studies were conducted in China, which somewhat limits the generalisability of the findings. However, the extant literature on physical activity and mental health outcomes is supportive of this relationship: physical activity and mental health (69)(70)(71)(72)(73). COVID-19 is an ongoing pandemic that may affect physical activity patterns and sedentary time in the longer-term (74). These results highlight the need for interventions to keep children and adolescents active and fit during the pandemic (74,75). A number of systematic reviews and meta-analyses assessing the potential of school-based interventions have reported physical activity as a positive and promising strategy to improve child and adolescent mental health (73,76,77); however, an alternative approach in the context of a pandemic should be investigated since so many stay-at-home orders are intermittently in place.
Another protective factor identified in the review that could be considered as an intervention target is parental self-efficacy (36). Conversely, parental mental health problems were associated with poorer outcomes among children and adolescents (7,16,25,37,48). Morelli et al. (36) make the case that, although parents are likely to be exposed to high levels of stress during the pandemic period, support can be offered in how to introduce daily structure and promote positive emotional functioning in their children. There are evidence-based parenting programs that cover these topics (78). Guidance on how to talk to children about the COVID-19 pandemic, including the loss of loved ones, has been published (79) as well as a picture book to read together with children (80).
Spending more time using social media and reading the news had a strong negative association with mental health outcomes (9). Some of the studies discussed that feeling lonely and anxious motivated children and adolescents to use social media more often mainly to cope with the situation and with the lack of social contact; however, it resulted in even more negative feelings of anxiety, depression and loneliness (43). An aspect related to this that should be considered more generally is screen use (81). Excessive screen use is known to impact on sleep and physical activity (82) and has been linked with poorer language skills, lower school performance and classroom engagement, social/emotional difficulties, and reduced psychological wellbeing (81). Although screen media use among children and adolescents can be used with positive intentions, such as for education or to interact with friends and family and can award parents time to complete necessary tasks, it is an area of concern, especially during the COVID-19 pandemic (81,83). Research on online social network site (SNS) addiction, such as excessive and compulsive online social networking, is growing (84). Not being a formally recognised diagnosis, well-documented therapeutic interventions are difficult to find. However, interventions and preventive efforts proven effective for other addictive behaviours, such as self-help strategies and therapies, can be applied to SNS addiction (84). In 2019, WHO released guidelines (85) stating that screen time is not recommended for children 1 year or under and for children 2-4 years old, the daily sedentary screen time should not be more than 1 h. Reading and storytelling are promoted as alternative sedentary activities (85).
This review comes with some limitations. Certain requirements that are placed on a more comprehensive systematic review, e.g., that the relevance of all studies must be checked by two independent reviewers, were omitted to be able to compile the findings from the literature in an efficient manner. This entails limitations in both accuracy and the scope of the material. Most of the included studies had a cross-sectional design, and therefore the direction of the association cannot be inferred, as the results do not provide knowledge about causation, but only about mathematical relationships. Yet, the second search performed to update the review with a particular focus on longitudinal studies can be considered a strength. Other methodological limitations of the studies include common use of convenience sampling, parent report in place of direct report in several studies, as well as a lack of validated outcome measures in some studies. Finally, the heterogeneity of the included studies and geographical variation limits comparability, and negates the possibility of meta-analysis. Therefore, only narrative description of the study findings was provided in the review. For all the above limitations, the results should be interpreted with caution. As more studies are added to the body of literature, the formation of the evidence could shift. This overview should therefore be seen as a "snapshot" of the current literature.

CONCLUSIONS
Due to the methodological heterogeneity of the studies included in this scoping review, as well as the low number of longitudinal studies and geographical variation, it is challenging to draw definitive conclusions about the real impact of the COVID-19 pandemic and societal infection control measures on the mental health of children and adolescents. However, the existing body of research gives some insight to potential protective and harmful factors that can be used to inform how parents, clinicians and policy makers can take action to mitigate the effects of the pandemic. From the protective and harmful factors identified in the scoping review, some potential intervention targets have been identified. Namely, interventions to promote physical activity and reduce screen time among children and adolescents, as well as parenting support programs to increase parental self-efficacy and promote positive and warm parent-child relationships.

AUTHOR CONTRIBUTIONS
AS conceived the idea for the literature search. JM led on designing the search, with support from GW. JM led on conducting the literature search and analysing the data. GW, NJ, and AS contributed to the interpretation of the data. JM and GW wrote the first draft of the manuscript. NJ and AS critically revised the manuscript for important intellectual content. All authors contributed to and have approved the final manuscript.