Early life-course environmental exposures and adolescent common mental illness in the UK: A 17-year follow-up study

Mental ill-health often emerges during adolescence, and the environments in which children grow up may shape this risk. Still, evidence is limited to single environmental exposures, urban samples, and short follow-ups. We investigated how built, social and chemical environments across childhood relate to common mental illness in adolescence, and whether associations differ by population density. Data were drawn from the Millennium Cohort Study, a nationally representative cohort born in 2000/2002 in the UK. High-resolution environmental data was linked to home addresses at birth and ages 3, 5, 7, 11, 14 and 17. Psychological distress (Kessler-6) and doctor diagnosed depression or serious anxiety were assessed at age 17. Confounder-adjusted and weighted generalized linear mixed models were fitted for single and domain-specific exposures. At age 17, ∼16% of participants had high psychological distress and ∼ 10.5% had been diagnosed with depression or anxiety (n = 7769-8374). Built and social environment from early childhood onwards (5 year: OR = 1.22 [95% CI: 1.07-1.39]; 7 year: OR = 1.16 [1.02, 1.33]; 11 year: OR = 1.15 [1.01-1.30]; 17 year: OR = 1.22 [1.05-1.39]; accumulation: OR = 1.21 [1.05-1.39])-especially lower greenness, greater distance to green space, more grey space, higher area deprivation and crime-were associated with high psychological distress, and, to a lesser extent, with diagnosis. Living close to the sea was associated with higher likelihood of common mental disorder, particular their diagnosis. Findings on air pollution were inconclusive. Associations with built and social environments were stronger in rural areas. Built and social environments in childhood and adolescence were significant correlates of adolescent common mental disorders. Future studies and interventions should consider urban/rural differences and timing of exposure.