Child and Adolescent Psychological Reactions to Climate Change: A Narrative Review Through an Existential Lens.

PURPOSE OF REVIEW: A narrative review was conducted on research surrounding children's and adolescents' experiences of emotional and mental health and wellbeing in relation to climate change; we also explored potential connections to existential themes. RECENT FINDINGS: Children and adolescents represent a vulnerable group in relation to experiencing negative mental health impacts due to climate change. Further, this population experiences a wide range of emotions in relation to climate change, with most research reporting on worry and anxiety. Several studies that explored associations between such emotions and mental health outcomes found positive associations. Additionally, research suggests that there is an existential underpinning to how climate change is experienced by children and adolescents. Although important contributions have been made in recent years, knowledge gaps remain. An understanding of the psychological responses children and adolescents have in relation to climate change is needed to inform practice and policy. This may be supported by an existential framework.

Item response theory and differential test functioning analysis of the HBSC-Symptom-Checklist across 46 countries.

BACKGROUND: The Symptom Checklist (SCL) developed by the Health Behaviour in School-aged Children (HBSC) study is a non-clinical measure of psychosomatic complaints (e.g., headache and feeling low) that has been used in numerous studies. Several studies have investigated the psychometric characteristics of this scale; however, some psychometric properties remain unclear, among them especially a) dimensionality, b) adequacy of the Graded Response Model (GRM), and c) measurement invariance across countries. METHODS: Data from 229,906 adolescents aged 11, 13 and 15 from 46 countries that participated in the 2018 HBSC survey were analyzed. Adolescents were selected using representative sampling and surveyed by questionnaire in the classroom. Dimensionality was investigated using exploratory graph analysis. In addition, we investigated whether the GRM provided an adequate description of the data. Reliability over the latent variable continuum and differential test functioning across countries were also examined. RESULTS: Exploratory graph analyses showed that SCL can be considered as one-dimensional in 16 countries. However, a comparison of the unidimensional with a post-hoc bifactor GRM showed that deviation from a hypothesized one-dimensional structure was negligible in most countries. Multigroup invariance analyses supported configural and metric invariance, but not scalar invariance across 32 countries. Alignment analysis showed non-invariance especially for the items irritability, feeling nervous/bad temper and feeling low. CONCLUSION: HBSC-SCL appears to represent a consistent and reliable unidimensional instrument across most countries. This bodes well for population health analyses that rely on this scale as an early indicator of mental health status.

Time trends in schoolwork pressure among Dutch adolescents, 2001-2017: Gender and educational differences.

AIMS: This study investigated gender and educational differences in trends in schoolwork pressure between 2001 and 2017 in nationally representative samples of Dutch adolescents in secondary education. METHODS: Data from five surveys of the Dutch Health Behaviour in School-aged Children study were used. RESULTS: Across the surveys, an increase in perceived schoolwork pressure was observed. Girls and adolescents enrolled in the higher educational levels reported higher levels of perceived schoolwork pressure and the strongest increase in schoolwork pressure over time. Especially for girls, there was a stronger increase in schoolwork pressure for those enrolled in higher educational tracks. CONCLUSIONS: Increases in schoolwork pressure over time were stronger among Dutch girls and students in the higher educational levels. Over time, schoolwork pressure increased most among girls in the highest educational levels. Explanations and implications for these results are discussed.

Mental Health in Adolescents with a Migration Background in 29 European Countries: The Buffering Role of Social Capital.

Previous research is inconclusive as to whether having an immigration background acts as a risk factor for poor mental health in adolescents, and furthermore, what contribution the social context in which adolescents grow up may make. To address these questions, the current study uses an integrative resilience framework to investigate the association between immigration background and adolescent mental health, and the moderating role of social capital at the individual, the school, and the national level. The study uses data gathered from nationally representative samples of adolescents aged 11, 13, and 15 years (Ngirls = 63,425 (52.1%); Mage = 13.57, SD = 1.64) from 29 countries participating in the 2017/18 Health Behaviour in School-aged Children (HBSC) study. Data analysis reveals that first- and second-generation immigrants reported higher levels of life dissatisfaction and psychosomatic symptoms than their native peers, and that this association varied across schools and countries. In addition, social capital was found to moderate the association between immigration background and adolescent mental health. Individual-level social support from peers and family and national-level trust protected against poor mental health in adolescents with an immigration background, while the opposite was true for individual-level teacher support. Supportive teacher-student relationships were found to provide more protection against poor mental health for native adolescents than for immigrant adolescents. Our findings indicate the importance of taking an ecological approach to design interventions to reduce the negative effects of having an immigration background on adolescent mental health.

Time trends in adolescent mental wellbeing in the Czech Republic between 2002 and 2018: gender, age and socioeconomic differences.

OBJECTIVES: Recent literature indicates a decline over time in adolescent mental wellbeing but results are inconsistent and rely mainly on data from Western societies. This study investigates time trends in adolescent mental wellbeing (psychological and somatic complaints, life satisfaction) among Czech adolescents and explores the moderating role of gender, age and socioeconomic status. METHODS: Nationally representative data from 29,376 Czech adolescents (50.8% girls, mean age = 13.43; SD = 1.65) across five Health Behaviour in School-aged Children (HBSC) surveys (2002, 2006, 2010, 2014, 2018) were used. Hierarchical regression models estimated national trends in adolescent mental wellbeing and established the moderating role of gender, age and socioeconomic status. RESULTS: From 2002 to 2018, an increase in the psychological complaints was observed. Life satisfaction decreased over time up to 2014 only, whereas somatic symptoms increased until 2010, followed by a decline in 2014 and 2018. Girls, older adolescents and those from low family affluence reported poorer mental wellbeing. Gender gap increased over time for psychological complaints and life satisfaction. Socioeconomic inequalities gap remained stable over the investigated timeframe. CONCLUSIONS: Our findings do not provide evidence for substantial temporal changes in mental wellbeing among adolescents in the Czech Republic. Yet, the increase in psychological complaints has been consistent which is an indicator of a small decline over time in adolescent mental wellbeing. Furthermore, the gender gap in mental wellbeing increased over time, whereas the age and socioeconomic differences remained relatively stable. This calls for the attention of public health professionals and policy makers from the Czech Republic.

Love and Dating Patterns for Same- and Both-Gender Attracted Adolescents Across Europe.

Sexual orientation is a multidimensional phenomenon, which includes identity, behavior, and attraction. The attraction component, however, is less studied than the other two. In this article, we present the development of a two-item measure to identify adolescents who prefer same- and both-gender partners for love and dating. The questions were administered to nationally representative samples of 15-year-old adolescents in eight European countries and regions participating in the Health Behaviour in School-aged Children (HBSC) cross-national study. The distribution of attraction, as operationalized by preference for the gender of love and dating partners, was similar across countries. These questions offer an alternative or supplementary approach to identify same- and both-gender attracted youth, without administering questions related to sexual identity.

Trends in the sexual behaviour of 15-year olds in Scotland: 2002-14.

Background: Early sexual initiation and inadequate contraceptive use can place adolescents at increased risk of unplanned pregnancy and sexually transmitted infections. These behaviours are patterned by gender and may be linked to social inequalities. This paper examines trends in sexual initiation and contraceptive use by gender and family affluence for Scottish adolescents. Methods: Cross-sectional data from four nationally representative survey cycles (2002, 2004, 2010, 2014) (n = 8895) (mean age = 15.57) were analysed. Logistic regressions examined the impact of survey year on sexual initiation, condom use and birth control pill (BCP) use at last sex; as well as any changes over time in association between family affluence and the three sexual behaviours. Analyses were stratified by gender. Results: Between 2002 and 2014, adolescent males and females became less likely to report having had sex. Low family affluence females were more likely to have had sex than high family affluence females, and this relationship did not change over time. Condom use at last sex was reported less by males since 2002, and by females since 2006. Low family affluence males and females were less likely to use condoms than high family affluence participants, and these relationships did not change over time. There were no effects of time or family affluence for BCP use. Conclusion: There has been a reduction in the proportion of 15-year olds in Scotland who have ever had sex, but also a decrease in condom use for this group. Economic inequalities persist for sexual initiation and condom use.

Sexual Health questions included in the Health Behaviour in School-aged Children (HBSC) Study: an international methodological pilot investigation.

BACKGROUND: This paper describes the methodological developments of the sexual health items included in the Health Behaviour in School-aged Children (HBSC) study since their mandatory inclusion in the study in 2002. The current methodological, ethical and pedagogical challenges in measuring young people's sexual health behaviours are discussed along with the issues associated with the sexual health items introduced to the HBSC study in 2002. The development and piloting of new cross-national items for use in the 2013/14 HBSC data collection are presented and discussed. METHODS: An international pilot study was undertaken to determine the impact of these proposed changes. Questionnaires and classroom discussion groups were conducted in five pilot countries in 2012/2013 (France, Hungary, Ireland, Portugal and Romania) with a total of 612 school-aged children (age M = 15.55 years, SD = 0.95). RESULTS: The majority of participants in each country provided positive feedback about the appropriateness of the questions. Some small cross-national differences were found in the self-reported quantitative data relating to the appropriateness of the questions (χ2 = 22.831, df = 9, p = .007, V = .117). Qualitative feedback suggests that for the vast majority of students the phrasing and age-targeting of the questions were considered appropriate. With the exception of a small number of respondents who commented on the clarity and/or personal nature of the content, no specific issues with the questions were identified. CONCLUSIONS: These findings provide guidance on the answerability (including the extent of missing and inconsistent data), understandability, acceptability (including in different cultures) and relevance of questions to potential participants. The findings from the pilot study suggest that in general, the questions are understandable, acceptable, and of a high priority to the target population, and that the simplification has significantly reduced the proportion of missing data. The new developments thus enhance the capacity of the questions to measure cross-nationally, sensitive aspects of young people's sexual behaviour. These questions were included in the 2013/2014 round of the HBSC survey and will continue to be used to monitor trends in adolescent sexual health and behaviours, and to inform and influence health services and health education policy and practice at local, national and international levels.

Cross-national time trends in bullying victimization in 33 countries among children aged 11, 13 and 15 from 2002 to 2010.

BACKGROUND: Bullying among children and adolescents is a public health concern; victimization is associated with psychological and physical health problems. The purpose of this study is to examine temporal trends in bullying victimization among school-aged children in Europe and North America. METHODS: Data were obtained from cross-sectional self-report surveys collected as part of the Health Behaviour in School-aged Children (HBSC) study from nationally representative samples of 11-, 13- and 15-year-olds, from 33 countries and regions which participated in the 2001-02, 2005-06 and 2009-10 surveys. Responses from 581 838 children were included in the analyses. Binary logistic regression was used for the data analyses. RESULTS: The binary logistic regression models showed significant decreasing trends in occasional and chronic victimization between 2001-02 and 2009-10 across both genders in a third of participating countries. One country reported significant increasing trends for both occasional and chronic victimization. Gender differences in trends were evident across many countries. CONCLUSION: Overall, while still common in many countries, bullying victimization is decreasing. The differences between countries highlight the need to further investigate measures undertaken in countries demonstrating a downward trend.

School socioeconomic status and psychological complaints among adolescents in 44 countries: The mediating role of schoolwork pressure and classmate support and the moderating role of family SES and country-level income inequality.

Previous research has reported both positive and negative associations between school socioeconomic status (SES) and internalizing problems among adolescents. Little is known about cross-national differences in this association, as well as potential mediators and moderators. Therefore, this study investigated this association using representative cross-national samples of adolescents whilst exploring the mediating role of schoolwork pressure and classmate support, and the moderating role of family SES and country-level income inequality. Using data from adolescents aged 11-15 from 44 countries, participating in the 2017/2018 Health Behaviour in School-aged Children (HBSC) study (N = 202,202), we employed multilevel regression models with cross-level interactions. School SES was operationalized as the average family affluence of adolescents within a school and psychological complaints (e.g., feeling low/depressed) were used as an indication of internalizing problems. On average across countries, adolescents in higher SES schools reported more psychological complaints, with a large effect size. However, differences in this association were observed across countries, with a positive association in 19 out of 44 countries, a negative association in one country, and nonsignificant associations in the remaining countries. Schoolwork pressure partially mediated the average association between school SES and psychological complaints, as school SES was positively associated with schoolwork pressure which was associated with more psychological complaints. Our results did not support the mediating role of classmate support. Also, we found a moderating effect of family SES, indicating a stronger positive association between school SES and psychological complaints for those with a below average family SES compared to those with an average and above average family SES. No moderating effect was observed for country-level income inequality. These findings suggest that adolescents with low family SES attending higher SES schools are especially at risk for psychological complaints, and may therefore require tailored support. A promising strategy to reduce psychological complaints entails addressing schoolwork pressure.

Adolescents perception of the COVID-19 pandemic restrictions and associated mental health and well-being: gender, age and socioeconomic differences in 22 countries.

BACKGROUND: The COVID-19-pandemic has had a profound impact on the lives of adolescents worldwide. This study examined the subjective perception of the COVID-19 pandemic measures and its association with mental health and well-being (i.e., loneliness, life satisfaction and multiple health complaints) among 13- and 15-years-old adolescents from 22 countries. METHODS: Data from the cross-national Health Behaviour in School-aged Children (HBSC) 2021/22 study were used from representative samples of 22 countries (N = 67,544; 51.9% girls). The self-perceived impact of COVID-19 measure comprised 10 items asking about the impact on several dimensions of adolescent lives (e.g., relationships with family and friends, health, or eating behaviours). Measures of loneliness, multiple health complaints, and life satisfaction were included as indicators of mental health and well-being. A non-parametric multilevel latent class analysis considering individual and country-levels was conducted to identify classes of self-perceived impact of the COVID-19 measures. Multilevel logistic regression models adjusted by age and socioeconomic status were applied to assess the association between COVID-19 measure impact classes and mental health. RESULTS: Three classes were identified on individual level encompassing a neutral (51%), positive (31%), or negative (18%) perception of COVID-19 measures. A third of the adolescents reported a positive impact of the pandemic measures. The distribution of classes was heterogeneous within and across countries. Within the positive COVID-19 measure impact class, social relationships were the most important dimension, whereas mental health problems were mostly represented within the negative COVID-19 measure impact class. Girls with a negative perception of pandemic measures showed higher levels of loneliness and multiple health complaints and lower life satisfaction. 15-year-old adolescents and those with a low socioeconomic status reported higher levels of loneliness and lower life satisfaction. CONCLUSIONS: The majority of adolescents perceived the pandemic measures as neutral or positive. Girls, 15-year-old adolescents, and those with low socioeconomic status were at higher risk of suffering from pandemic measures and associated problems of loneliness, multiple health complaints, and low life satisfaction. We conclude that adolescent's mental health and well-being should be considered in the decision-making process by ensuring that the unique challenges of adolescents are adequately addressed in policies.

Measuring negative emotional responses to climate change among young people in survey research: A systematic review.

BACKGROUND: Climate change is a threat to the mental and emotional wellbeing of all humans, but young people are particularly vulnerable. Emerging evidence has found that young people's awareness of climate change and the danger it poses to the planet can lead to negative emotions. To increase our understanding about this, survey instruments are needed that measure the negative emotions young people experience about climate change. RESEARCH QUESTIONS: (1) What survey instruments are used to measure negative emotional responses to climate change in young people? (2) Do survey instruments measuring young people's negative emotional responses to climate change have evidence of reliability and validity? (3) What factors are associated with young people's negative emotional responses to climate change? METHODS: A systematic review was conducted by searching seven academic databases on November 30, 2021, with an update on March 31, 2022. The search strategy was structured to capture three elements through various keywords and search terms: (1) negative emotions, (2) climate change, and (3) surveys. RESULTS: A total of 43 manuscripts met the study inclusion criteria. Among the 43 manuscripts, 28% focused specifically on young people, while the other studies included young people in the sample but did not focus exclusively on this population. The number of studies using surveys to examine negative emotional responses to climate change among young people has increased substantially since 2020. Survey instruments that examined worry or concern about climate change were the most common. CONCLUSION: Despite growing interest in climate change emotions among young people, there is a lack of research on the validity of measures of such emotions. Further efforts to develop survey instruments geared to operationalize the emotions that young people are experiencing in relation to climate change are needed.

Encouraging greater empowerment for adolescents in consent procedures in social science research and policy projects.

The United Nations Convention on the Rights of the Child emphasizes the importance of allowing children and adolescents to influence decisions that are important to them following their age and maturity. This paper explores the principles, practices, and implications around using parental versus child/adolescent consent when participating in social science research and policy development. Experiences from two studies are presented: The Confronting Obesity: Co-creating policy with youth (CO-CREATE) and the Health Behaviour in School-aged Children (HBSC) study, a World Health Organization (WHO) Collaborative Cross-National study. Although parental consent may be an important gatekeeper for protecting children and adolescents from potentially harmful research participation, it may also be considered an obstacle to the empowerment of children and adolescents in case they want to share their views and experiences directly. This paper argues that evaluation of possible harm should be left to ethics committees and that, if no harm related to the research participation processes is identified and the project has a clear perspective on collaborating with the target group, adolescents from the age of 12 years should be granted the legal capacity to give consent to participate in the research project. Collaboration with adolescents in the development of the research project is encouraged.

Measurement Invariance of the WHO-5 Well-Being Index: Evidence from 15 European Countries.

(1) Background: The World Health Organization (WHO)-5 Well-Being Index has been used in many epidemiological studies to assess adolescent mental well-being. However, cross-country comparisons of this instrument among adolescents are scarce and, so far, no good-fitting, common invariant measurement model across countries has been reported. The present study aims to evaluate and establish a version of the WHO-5 Well-Being Index that allows for a valid cross-country comparison of adolescent self-reported mental well-being. (2) Methods: Using data from the 2018 Health Behaviour in School-aged Children study, we evaluated the measurement model and measurement invariance of the five items of the WHO-5 Well-Being Index. We used nationally representative samples of 11-, 13-, and 15-year-old adolescents (N = 74,071) from fifteen countries and regions in Europe. Measurement invariance of the WHO-5 was assessed using a series (country, gender, and age) of multi-group confirmatory factor analyses. In addition, we evaluated the convergent validity of the measure by testing its correlations with psychosomatic complaints, life satisfaction, and self-rated health. (3) Results: We found that WHO-5 does not show good psychometric properties or good measurement invariance fit. However, by excluding the first item of the scale ("I have felt cheerful and in good spirits"), the WHO-4, consisting of the other four original items, had good psychometric properties, and demonstrated good suitability for cross-national comparisons (as well as age and gender) in adolescent mental well-being. (4) Conclusions: The present study introduces the WHO-4-a revised version of the WHO-5-, that allows for a valid comparison of mental well-being across fifteen countries and regions in Europe. The WHO-4 proved to be a reliable and valid instrument to assess mental well-being in the adolescent population.

The Mental Well-Being of Italian Adolescents in the Last Decade through the Lens of the Dual Factor Model.

(1) Background: In Italy, the components of adolescents' mental well-being (psychological symptomatology and cognitive perception of life satisfaction) showed different temporal trends, suggesting the adoption of a multidimensional conceptualization. We aimed to assess temporal patterns and provide additional insights into Italian adolescents' mental well-being in the last decade by adopting the Dual Factor Model; (2) Methods: We used nationally representative samples of Italian students (n = 165,000) aged 11, 13, and 15 years across the three more recent Italian Health Behaviour in School-aged Children (HBSC) surveys. Two measures of mental well-being were used: life satisfaction (LS, indicator of positive subjective well-being) and psychological health complaints (PHC, indicator of mental illness); (3) Results: Our study showed that the overall sample has been moving from a Complete Mental Health (Flourishing) to an Incomplete Mental Illness (Struggling) condition. Among 13- and 15-year-old girls, a jump from one to the other mental condition was observed in the 2014-2018 and 2010-2014 time periods, respectively; (4) Conclusions: Our findings suggest that Italian adolescents, especially older girls, have been shifting from Complete Mental Health to Incomplete Mental Illness in the last decade. Further research is needed to investigate this breaking up of the connection between psychological symptomatology and cognitive perception of life satisfaction.

Structural gender inequality and gender differences in adolescent substance use: A multilevel study from 45 countries.

-Societal gender inequality relates to gender differences in adolescent substance use.-The gender gap in adolescent substance use is larger in countries with higher levels of gender inequality.-Girls in these countries were less likely to get drunk, use alcohol or smoke cigarettes than boys.

Measuring negative emotional responses to climate change among young people in survey research: a systematic review protocol.

INTRODUCTION: Many young people report experiencing negative emotional responses to their awareness of climate change and the threats it poses to their future. With that, an increasing number of survey instruments have been developed to examine young people's negative emotional responses to their awareness of climate change. This report describes a protocol for a systematic review that aims to identify, synthesise and critically appraise how negative emotional responses to climate change among young people have been measured in survey research. The research questions addressed in this review are: (1) How has negative emotional responses to climate change been defined and measured among young people? (2) How do survey instruments measuring young people's negative emotional responses to climate change vary in terms of reliability and validity? (3) What factors are associated with negative emotional responses to climate change among young people? METHODS AND ANALYSIS: Seven academic databases (CINAHL, ERIC, MEDLINE, PsycINFO, Web of Science, Scopus, and Environment Complete) will be searched to retrieve studies published between 1 January 2006 and 31 March 2022 and published in English. Studies including survey instruments that measure negative emotional responses among young people (aged 10-24 years) will be eligible for inclusion. Targeted journals will be hand-searched. This review will follow Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines for systematic reviews. The methodological quality, in terms of reliability and validity, of the included studies will be assessed using the Consensus-based Standards for the Selection of Health Measurement Instruments (COSMIN) checklist for risk of bias of patient-reported outcome measures. To rate the quality of the instruments, we will use a modified Grading of Recommendations, Assessment, Development and Evaluations technique defined by the COSMIN guidelines. ETHICS AND DISSEMINATION: Ethical approval is not applicable for this study. We will disseminate the findings through publication in peer-reviewed journals and presentations. PROSPERO REGISTRATION NUMBER: CRD42022295733.

Gender Differences in Bullying Reflect Societal Gender Inequality: A Multilevel Study With Adolescents in 46 Countries.

PURPOSE: Social patterns in bullying show consistent gender differences in adolescent perpetration and victimization with large cross-national variations. Previous research shows associations between societal gender inequality and gender differences in some violent behaviors in adolescents. Therefore, there is a need to go beyond individual associations and use a more social ecological perspective when examining gender differences in bullying behaviors. The aim of the present study was twofold: (1) to explore cross-national gender differences in bullying behaviors and (2) to examine whether national-level gender inequality relates to gender differences in adolescent bullying behaviors. METHODS: Traditional bullying and cyberbullying were measured in 11-year-olds to 15-year-olds in the 2017/18 Health Behaviour in School-aged Children study (n = 200,423). We linked individual data to national gender inequality (Gender Inequality Index, 2018) in 46 countries and tested their association using mixed-effects (multilevel) logistic regression models. RESULTS: Large cross-national variations were observed in gender differences in bullying. Boys had higher odds of perpetrating both traditional and cyberbullying and victimization by traditional bullying than girls. Greater gender inequality at country level was associated with heightened gender differences in traditional bullying. In contrast, lower gender inequality was associated with larger gender differences for cyber victimization. DISCUSSION: Societal gender inequality relates to adolescents' involvement in bullying and gendered patterns in bullying. Public health policy should target societal factors that have an impact on young people's behavior.

Bullying, Mental Health, and the Moderating Role of Supportive Adults: A Cross-National Analysis of Adolescents in 45 Countries.

Objectives: Relationships with supportive adults during adolescence may be a protective factor that lowers the risks associated with bullying. The current study aimed to examine the moderating role of supportive adults in the associations between bullying involvement (in-person and cyber) and mental health problems (psychological symptoms and low life satisfaction). Methods: Data from 45 countries and regions taking part in the 2017/18 Health Behaviour in School-Aged Children study (N = 230,757) were used. Multivariable Poisson regression models were used to estimate relative risks of bullying on mental health. Effect estimates were compared across the number of supportive adults to examine a possible cumulative protective effect of relationships with supportive adults. Results: Bullying involvement was consistently associated with poor mental health across the 45 countries. Risk of mental health problems associated with bullying involvement was greatest among students reporting relationships with multiple supportive adults. This was true for all indicators of bullying involvement. Conclusion: Bullying remains a prevalent and harmful experience for youth worldwide. Merely having supportive adults is not sufficient in protecting youth from experiencing the mental health risks associated with bullying.

Cross-national validation of the social media disorder scale: findings from adolescents from 44 countries.

BACKGROUND AND AIMS: There is currently no cross-national validation of a scale that measures problematic social media use (SMU). The present study investigated and compared the psychometric properties of the social media disorder (SMD) scale among young adolescents from different countries. DESIGN: Validation study. SETTING AND PARTICIPANTS: Data came from 222 532 adolescents from 44 countries participating in the health behaviour in school-aged children (HBSC) survey (2017/2018). The HBSC survey was conducted in the European region and Canada. Participants were on average aged 13.54 years (standard deviation = 1.63) and 51.24% were girls. MEASUREMENT: Problematic SMU was measured using the nine-item SMD scale with dichotomous response options. FINDINGS: Confirmatory factor analyses (CFA) showed good model fit for a one-factor model across all countries (minimum comparative fit index (CFI) and Tucker-Lewis index (TLI) = 0.963 and 0.951, maximum root mean square error of approximation (RMSEA) and standardized root mean square residual (SRMR) = 0.057 and 0.060), confirming structural validity. The internal consistency of the items was adequate in all countries (minimum alpha = 0.840), indicating that the scale provides reliable scores. Multi-group CFA showed that the factor structure was measurement invariant across countries (ΔCFI = -0.010, ΔRMSEA = 0.003), suggesting that adolescents' level of problematic SMU can be reliably compared cross-nationally. In all countries, gender and socio-economic invariance was established, and age invariance was found in 43 of 44 countries. In line with prior research, in almost all countries, problematic SMU related to poorer mental wellbeing (range ßSTDY = 0.193-0.924, P < 0.05) and higher intensity of online communication (range ßSTDY = 0.163-0.635, P < 0.05), confirming appropriate criterion validity. CONCLUSIONS: The social media disorder scale appears to be suitable for measuring and comparing problematic social media use among young adolescents across many national contexts.