Multilayered childhood adversity and mortality: a population-based cohort study of 1.2 million individuals

Background: Childhood adversity is multi-layered, extending beyond the family to include broader neighbourhood and health contexts. We aimed to investigate how these multiple layers of childhood adversity relate to the risk of death in young adulthood. Methods: Children were followed from birth into young adulthood (16–42 years) using nationwide register data on multi-layered childhood adversity and mortality. Individual adversity included perinatal adversity (preterm or small-for-gestational-age) and mental and physical health-service use. Family adversity included five distinct groups using group-based multi-trajectory modelling based on 12 adversities. Neighbourhood adversity included material deprivation in small-area geographical zones. We evaluated associations of these layers with all-cause mortality using survival analyses. Findings: 1,235,519 individuals born between 1980 and 2001 were followed up until 31 December 2022, capturing 7320 deaths. Children facing high family adversity were more likely to have perinatal adversity, use health services, and live in deprived neighbourhoods. Each layer was separately associated with mortality; for example, high physical health-service use (HR: 2.36; 95% CI: 2.24; 2.48), corresponding to 42 (39; 45) excess deaths per 100,000 person-years (PY), while living in a deprived neighbourhood (HR: 1.20; 95% CI: 1.14; 1.26), corresponding to 8 (6; 11) excess deaths per 100,000 PY. Cross-layer additive interactions were strongest between family adversity and child health or perinatal adversity. For example, high physical health-service use combined with high family adversity were associated with 194 excess deaths (95% CI: 172–216) per 100,000 PY with an estimated 106 due to cross–layer interaction (P < 0.0001). The highest mortality risk was observed amongst those with both high family and individual adversity: HR: 7.16 (95% CI: 6.40; 8.01) compared to those with low adversity. Interpretation: The co-occurrence and interaction of childhood adversities across different layers may create highly vulnerable groups, deepening lifelong health inequalities. This underscores the importance of a comprehensive, multi-layered approach that targets individual vulnerabilities as well as the broader social environment. Funding: The European Research Council.