Prospective association between adherence to dietary recommendations and incident depressive symptoms in the French NutriNet-Santé cohort

A posteriori healthier dietary patterns and several nutrients have been associated with lower risks of depression in various studies; however, evidence is lacking with regard to the prospective association between adherence to nutritional recommendations (food-based and nutrient-based recommendations) and incident depression or depressive symptoms. In this study, we investigate such associations in the NutriNet Santé cohort. The study sample included 26 225 participants (aged 18-86 years) who were initially free of depressive symptoms. Adherence to nutritional recommendations was measured by four scores namely modified French Programme National Nutrition Santé-Guideline Score (mPNNS-GS), Alternative Healthy Eating Index-2010 (AHEI-2010), Probability of Adequate Nutrient Intake Dietary Score (PANDiet) and Diet Quality Index-International (DQI-I), using non-consecutive dietary record data during the first 2 years of follow-up (mean number of recording days=8, sd 2). Depressive symptoms were defined by a Center for Epidemiologic Studies Depression Scale (CES-D) score ≥17 for men and ≥23 for women. We used Cox proportional hazards models to estimate hazard ratios and 95 % CI, modelling the dietary scores as standardised continuous variables and as tertiles. Over a mean follow-up of 6 years, we identified 2166 incident cases of depressive symptoms. All dietary scores with the exception of the AHEI-2010 were significantly inversely associated with incident depressive symptoms. In the fully adjusted model, an increase of 1 sd in the mPNNS-GS, PANDiet and DQI-I was, respectively, associated with an 8 % (95 % CI 4, 13), 5 % (95 % CI 1, 9) and 9 % (95 % CI 5, 13) reduction in the risk of depressive symptoms. Overall, these findings suggest that diet in accordance with national or international guidelines could have beneficial effects with regard to mental health.