Associations of dietary habits, inflammatory dietary index, and lifestyle factors with depressive symptoms: a cross-sectional study of 53,539 individuals with thyroid nodules

Background: Depressive symptoms are closely associated with thyroid nodules (TNs). Lifestyle and dietary factors have been linked to depressive symptoms. Therefore, this study aimed to investigate the associations between dietary patterns-including dietary diversity, protein-enriched dietary, inflammatory dietary patterns, dietary habits and depressive symptoms in individuals with TNs. Methods: This cross-sectional study included 53,539 participants who underwent physical examinations between January 2017 and March 2024. Participants completed self-reported questionnaires on demographic characteristics, physical health, activity levels, dietary index scores, dietary habits, and depressive symptoms. Results: Participants were female (OR: 1.38, 95 % CI: 1.30–1.46), divorced or widowed (OR: 1.56, 95 % CI: 1.31–1.85), had a higher waist-hip ratio, and (OR: 2.22; 95 % CI: 1.43–3.43) and engaged in prolonged sedentary time (OR: 1.51; 95 % CI: 1.41–1.62) were more likely to report depressive symptoms. Regarding dietary factors, an anti-inflammatory dietary (OR: 0.79; 95 % CI: 0.75–0.83) and a protein-enriched dietary (OR: 0.87; 95 % CI: 0.83–0.92) were associated with a lower risk of depressive symptoms. However, irregular eating (OR: 2.00, 95 % CI: 1.81–2.21), overeating frequently (OR: 1.87; 95 % CI: 1.70–2.05), and being a former drinker (OR: 1.43, 95 % CI: 1.19–1.71) were associated with a higher risk of depressive symptoms in individuals with TNs. Conclusions: Unhealthy eating behaviors and prolonged sedentary time were associated with a higher risk of depressive symptoms in individuals with TNs, while anti-inflammatory and protein-rich diets were associated with lower odds. These findings suggest potential links between dietary and lifestyle factors and depressive symptoms, which may warrant further investigation in prospective or interventional studies.