Associations between Global Burden of Disease dietary risk factors and depression in the REGICOR population-based cohort study

Background: We studied associations between dietary risk factors and depression outcomes in adults aged 35-79y from the population-based REGICOR cohort in Catalonia (Spain), following the Global Burden of Disease Lifestyle And Mental Disorder (GLAD) protocol (DERR1-10.2196/65576). Methods: This prospective observational study included participants for whom baseline dietary data (2003-2006) assessed with a validated 157-item food frequency questionnaire (FFQ) were available (N=6,352). Exposures included Global Burden of Disease (GBD)-defined dietary risk factors, specifically food groups (fruits, vegetables, legumes, whole grains, nuts & seeds, milk, red meat, processed meat, and sweet drinks) and nutrients (fibre, calcium, polyunsaturated fatty acids (PUFA), and sodium). Ultra-processed foods (UPFs), classified according to NOVA, were also included. Participants reporting antidepressant treatment use at baseline were excluded. Incident depression diagnoses (primary outcome, main analysis) were obtained from electronic health records until December 2016. In a subsample attending the second visit (2007-2013), the self-reported Patient Health Questionnaire (PHQ-9) was used to define moderate depressive disorders (score ≥10) and severe depressive disorder (score ≥15) (secondary outcomes). Cox proportional hazards and logistic regression models were applied. Results: Main analysis included 4,695 adults (47.4% women; mean age 56.4 [SD=12.6]). Over a median follow-up of 12.1 years, 256 (5.5%) participants developed depression. After adjustment, higher fibre intake was associated with lower depression incidence (HR _{per 5 g/day} : 0.912; 95% CI: 0.844–0.986). In contrast, greater consumption of sweet drinks (HR _{per 100 g/day} : 1.118; 95% CI: 1.043–1.199) and UPFs (UPF1: HR _{per 10%g/day} : 1.281; 95% CI: 1.097–1.496) was associated with increased risk. In secondary analyses (N=2,986), processed meat (OR _{per 10 g/day} : 1.078; 95% CI: 1.010–1.151), and UPFs intake (UPF1: OR _{per 10%g/day} : 1.308; 95% CI: 1.069–1.601) were associated with higher odds of depressive disorder. Only processed meat intake was associated with severe depressive disorder (OR _{per 10 g/day} : 1.129; 95% CI: 1.010–1.261). Conclusions: Sweet drinks, processed meat and UPFs were positively associated with depression outcomes, whereas higher fibre intake showed an inverse association. These results support dietary composition as a potentially modifiable risk factor for depression prevention and public health nutrition strategies.