Adverse childhood experiences and health-related outcomes in early adulthood: Evidence from the Korean Welfare Panel Study

•The period prevalence of one or more ACEs ranged from 53 % to 67 %.•Associations between ACEs and depressive symptoms were most robust in adolescence.•Associations between ACEs and chronic illness were only observed in early adulthood.•Depressive symptoms in adolescence partly mediated the link to adult depression.•Paths between ACEs and chronic illness in early adulthood were unmediated. Research has reliably shown that adverse childhood experiences (ACEs) are highly prevalent and consequential, though scientific progress has been hindered by the frequent use of retrospective, cross-sectional study designs. As a result, there is limited knowledge of when ACEs are most likely to occur, and there are lingering questions about causal inferences and effect sizes. This study aimed to estimate the period prevalence of ACEs in early-, mid-, and late-adolescence, and to compare crosssectional and longitudinal associations between ACEs and health-related outcomes in adolescence and early adulthood. Using a panel study of 353 participants and their caregivers from 2006 to 2021 in South Korea, eight ACEs were measured across three time periods: ages 10–12, 13–15, and 16–18. Descriptive analyses produced estimates of period prevalence, while correlational and path analyses generated direct and indirect associations between ACEs and health-related outcomes (chronic illness; depressive symptoms) in lateadolescence and early adulthood. Results showed that period prevalence estimates ranged from 53 % to 67 %. ACEs were associated with more robust effects on depressive symptoms in late adolescence than early adulthood and in cross-sectional analyses than longitudinal analyses. Conversely, significant associations with chronic illness were only observed prospectively in early adulthood. The link between ACEs and adult depressive symptoms was partly mediated by depressive symptoms in late adolescence, whereas paths between ACEs and adult chronic illness were unmediated. The findings confirm that ACEs are highly prevalent and harmful. Future ACE research should explore the extent to which findings are influenced by method effects.