Estimating prospective risk of depression associated with lifestyle factors: an 18-year cohort study using the EPIC-Norfolk Cohort

Background Depression is common in the UK, contributing significantly to global health burden. While lifestyle factors are promising prevention targets, their contribution to UK depression prevalence is underexplored. Clarifying this could guide prevention efforts. Methods This study used data from 18 years of the EPIC-Norfolk cohort (part of the European Prospective Investigation into Cancer and Nutrition; >30,000 participants recruited from 1993–1997), including four timepoints: first health check (1993-98), 18-month follow-up (1994-99), second (1998–2000), and third health checks (2004–2011). Prevalence of suboptimal lifestyle behaviours (diet, physical activity, smoking, and sleep), defined by Global Burden of Disease Study and UK LiveWell guidelines, was calculated. Prospective associations with depression risk (score < 52 on the mental-health component of the Short-Form 36 Health Questionnaire) were assessed using complete-case Poisson regression with robust standard errors, adjusting for age, sex, and socioeconomic status. Results Suboptimal dietary intake was highly prevalent across all timepoints. Insomnia (RR 2.44 versus no insomnia, 95%CI 1.86–3.21), current smoking (1.50 versus never, 1.13–1.98), and high dietary inflammatory index (1.12, 1.02–1.23) were associated with higher depression risk, whilst fibre (0.96 per gram, 0.92–0.99), vegetable intake (0.81 per 80g serve, 0.67–0.99), former smoking (0.65 versus current, 0.49–0.88), and self-reported physical activity (0.54 active versus inactive, 0.38–0.75) were associated with lower risk. Conclusions These results support previous work reporting suboptimal lifestyle behaviours (e.g. smoking) as associated with increased depression risk. Conversely, healthful lifestyle behaviours (i.e. increased fibre and vegetable intake, physical activity, smoking cessation) are associated with lower depression risk.