Social inequality in mental halth among 15-year-old adolescents in Denmark from 2002-2022

Abstract Background Poor mental health among adolescents and social inequality have risen simultaneously during the past 20 years, but the time trend in their associations remains unclear. The aim of this study is to examine whether social inequality in adolescent mental health has changed over the past two decades (2002-2022), by studying the associations between socioeconomic status (SES) and mental health measures among 15-year-old adolescents in Denmark. Methods This nationwide register-based cohort study consists of seven cross-sectional analyses of the associations between adolescents’ SES, defined as family income and parental educational level, and poor mental health, defined as mental disorder diagnoses and medication use, for seven 3-year-periods during 2002-2022. The population consists of all registered residents in Denmark who turned 15 years in the years between 2002 and 2022. All data were obtained from Danish population-based registers. The prevalence of mental health outcomes was calculated, and the associations between SES and mental health were analysed using adjusted log-binomial regression. Results The prevalence of mental disorder diagnoses and medication use among adolescents increased over time. Associations between SES and poor mental health were found between all SES measures during the period, with a trend toward decreasing associations for low-SES groups and stable odds ratios for high-SES groups compared to the middle-SES. The diagnosis-specific analyses showed different patterns, for example, increasing associations for SES and substance use disorders and decreasing associations for SES and mood disorders. Conclusions This study highlights persistent but evolving social inequalities in adolescent mental health in Denmark from 2002 to 2022. While the prevalence of mental health diagnoses increased, changes in inequality patterns were diagnosis-specific, suggesting that broader societal trends may influence types of mental disorders differently. Key messages • Although a decreasing trend of social inequality over time is observed, the need for targeted mental health interventions addressing social inequality remains. • The degree of social inequality varies by mental disorder diagnosis, e.g. with increasing trends for substance use and decreasing trends for mood disorders.