Although previous research has established a positive association between national income inequality and socioeconomic inequalities in adolescent health, very little is known about the extent to which national-level wealth inequalities (i.e., accumulated financial resources) are associated with these inequalities in health. Therefore, this study examined the association between national wealth inequality and income inequality and socioeconomic inequality in adolescents' mental well-being at the aggregated level. Methods: Data were from 17 countries participating in three consecutive waves (2010, 2014, and 2018) of the cross-sectional Health Behaviour in School-aged Children study. We aggregated data on adolescents' life satisfaction, psychological and somatic symptoms, and socioeconomic status (SES) to produce a country-level slope index of inequality and combined it with country-level data on income inequality and wealth inequality (n ¼ 244,771). Time series analyses were performed on a pooled sample of 48 country-year groups. Results: Higher levels of national wealth inequality were associated with fewer average psychological and somatic symptoms, while higher levels of national income inequality were associated IMPLICATIONS AND CONTRIBUTIONResearch has established the positive association between national income inequality and adolescent socioeconomic health inequalities, but little is known about national-level wealth inequalities (i.e., accumulated financial resources). This study linked national wealth and income inequality to socioeconomic inequalities in Conflicts of interest: B.D.C. is working for a financial company under supervision of the Financial Services and Markets Authority. The authors have no other conflicts of interest to disclose. Authors' contributions: B.D.C. and M.D. designed the study. M.D. had primary responsibility for writing and editing of the article and supervised the interpretation of the results. B.D.C. conceptualized and developed the wealth inequality indicator. D.W. and Y.Y.H. further improved the conceptualization of the wealth inequality indicator, collected reliable financial and economic data, and calculated the wealth inequality indicator. F.E. performed the analysis, and L.A. and N.L. interpreted the results. All authors critically reviewed the article. G.W.J.M.S. and C.C. made substantial and equal contributions to the writing of the whole article. All authors listed gave final approval for the article to be published. Disclosure: This supplement was supported by the World Health Organization European Office and the University of Glasgow. The articles have been peerreviewed and edited by the editorial staff of the Journal of Adolescent Health. The opinions or views expressed in this supplement are those of the authors and do not necessarily represent the official position of the funder.

Background Previous research established a positive association between national income inequality and socioeconomic inequalities in adolescent health, but little is known about the extent to which national level inequalities in accumulated financial resources (i.e. wealth) are associated with these health inequalities. Therefore, we examined the association between national wealth inequality and income inequality and socioeconomic inequalities in adolescent mental wellbeing. Methods Data were from 17 countries participating in three successive waves (2010, 2014 and 2018) of the cross-sectional Health Behaviour in School-aged Children (HBSC) study. We combined individual-level data on adolescents' life satisfaction, psychological and somatic symptoms and socioeconomic status (SES) with country-level data on income and wealth inequality (n = 244771). We performed time-series analysis on a pooled sample of 48 country/year groups. Results Higher levels of national wealth inequality were associated with fewer average psychological and somatic symptoms, while higher levels of national income inequality were associated with more psychological and somatic symptoms. No associations between either national wealth inequality or income inequality and life satisfaction were found. Smaller differences in somatic symptoms between higher and lower SES groups were found in countries with higher levels of national wealth inequality. In contrast, larger differences in psychological symptoms and life satisfaction (but not somatic symptoms) between higher and lower SES groups were found in countries with higher levels of national income inequality. Conclusions Although both national wealth and income inequality are associated with (socioeconomic inequalities in) adolescent mental wellbeing, associations are in opposite directions. Further research is warranted to gain better understanding in the role of national wealth inequality on (socioeconomic inequalities in) adolescent health. Key messages This is one of the first studies to examine if socioeconomic inequalities in adolescent mental wellbeing are associated with national wealth inequality independently from national income inequality. Opposing effects of national wealth inequality and income inequality on socioeconomic inequalities in adolescents’ mental wellbeing warrant further research before policy recommendations can be made.