Mathilde Brons ^1* Paola Berchialla ² Marco Helbich ¹ Maxim Dierckens ³ Michela Lenzi ⁴ Joanna C Inchley ⁵ Gonneke W J M Stevens ¹

• ¹ Utrecht University, Utrecht, Netherlands
• ² University of Turin, Turin, Piedmont, Italy
• ³ Ghent University, Ghent, East Flanders, Belgium
• ⁴ University of Padua, Padua, Veneto, Italy
• ⁵ University of Glasgow, Glasgow, Scotland, United Kingdom

Objectives: Cross-national differences in long-term trends in social inequalities in adolescent mental health remain poorly understood, as does the impact of societal changes. We tested (1) whether the association between family socioeconomic status and psychological and somatic complaints changed between 2002 and 2022, (2) the extent to which these trends varied across countries, and (3) whether changes in income inequality, schoolwork pressure, and internet activity within countries were related to these trends. Methods: Using data from 903,344 adolescents across 32 countries from the Health Behaviour in School-aged Children (HBSC) study between 2002 and 2022, we employed multilevel models to investigate the research questions. Results: We observed a nonlinear increase in psychological and somatic complaints over time. On average, social inequalities in both outcomes remained stable across countries, although the trends varied from one country to another. Only income inequality explained the differences between countries in these trends. In countries where income inequality increased over time, social inequalities in psychological complaints became smaller. Conclusions: Our study highlights ongoing global disparities in adolescents’ mental health problems, urging for more effective health policies.