Higher adherence to a Nordic diet is associated with reduced risk of mild depressive symptoms: a population-based analysis

Abstract Purpose Although the Mediterranean diet has been widely studied in relation to depression, less is known about the associations between other diets, such as the Nordic Diet, and depressive symptoms and clinical depression. The aim was to examine whether adherence to a Nordic diet (assessed with the modified Nordic Diet Index, mNDI) is associated with depressive symptoms and clinical depression in the Finnish Health 2000–2011 survey. Methods The cross-sectional data included 4697 adults, while the prospective data included 1788 participants for depressive symptoms and 1862 for depressive disorders. Depressive symptoms were assessed in 2000 using a composite variable derived from validated questionnaires, and in 2011 using the Beck Depression Inventory-13 (BDI-13). Clinical diagnoses were based on the Munich-Composite International Diagnostic Interview (M-CIDI) or self-report. Results At baseline, 1746 participants (37.2%) reported elevated depressive symptoms. Higher mNDI (indicating better adherence) was associated with 25.0% lower multivariable-adjusted odds of depressive symptoms (Q4 vs. Q1; 95% CI 8.6–38.5%, p-trend = 0.013). In the prospective analyses, higher mNDI was associated with lower odds of elevated depressive symptoms (BDI-13 cut-off scores 1 and 5), but these associations attenuated after full adjustment. No association was observed at the BDI-13 cut-off 9 (all p -values ≥ 0.303). Adherence to a Nordic diet was not associated with clinical depression. Conclusion Higher adherence to a Nordic diet was associated with fewer depressive symptoms and a reduced risk of elevated depressive symptoms, but not with clinical depression, possibly due to the limited number of cases diagnosed via M-CIDI or reported by participants ( n = 82).