Adherence to the Australian dietary guidelines and development of depressive symptoms at 5 years follow-up amongst women in the READI cohort study

BACKGROUND: Depression is the single largest contributor to global disability. There is growing evidence that a healthy diet is associated with reduced depression risk. However, beyond the Mediterranean diet, few longitudinal studies have explored the relationship between adherence to national dietary guidelines and depression. Hence, this study investigates the relationship between adherence to Australian Dietary Guidelines and depressive symptoms. METHODS: Data was drawn from the READI longitudinal study, a prospective cohort study of socioeconomically disadvantaged Australian women. This analysis includes a sub-sample of 837 women. A generalized linear model was used to explore whether baseline diet (assessed using the Dietary Guideline Index (DGI-2013; score range 0 to 85)) was associated with risk of developing depressive symptoms (measured by the Centre for Epidemiologic Studies Depression (CES-D)) at 5 years follow-up, whilst adjusting for potential confounders. A fixed-effects model was used to assess associations between concurrent changes in diet quality and depressive symptoms from baseline to 5 years follow-up. RESULTS: An association between baseline diet quality and risk of developing depressive symptoms at follow-up was observed, where a 10 unit increase in DGI-2013 score was associated with an estimated 12% lower risk of developing heightened depressive symptoms (RR = 0.875, 95%CI 0.784 to 0.978, p = 0.018). The fixed-effects model indicated that an increase in DGI score over 5 years follow-up was associated with a lower (improved) CES-D score (B = -0.044, 95% CI − 0.08 to − 0.01, p = 0.024). CONCLUSIONS: Our results provide evidence that better adherence to the Australian Dietary Guidelines may result in improved depressive symptoms. The growing high-quality evidence regarding the diet-depression relationship provides us with a rationale for developing strategies for supporting dietary behaviour change programs to lower depression rates.