This systematic review provides a comprehensive analysis of the relationship between various a priori diet quality indices and depressive outcomes. Longitudinal studies demonstrate a strong association between adherence to a Mediterranean diet and a reduced risk of depression, as well as an inverse relationship between pro-inflammatory diets and depression. Similar trends are observed with the Healthy Eating Index and other country-specific dietary guidelines.

The researchers acknowledge there’s considerable variability in how depression and dietary patterns are assessed across studies, with most focusing on depressive symptoms rather than clinically diagnosed depression. The accuracy and comparability of the studies are impacted by factors like the diverse assessment tools used, reliance on self-reported dietary data, and varying statistical adjustments across studies. Additionally, most research is from high-income countries, limiting the generalizability of findings to low-and-middle-income countries. Despite these limitations, the review highlights observational evidence suggesting that healthy diets, particularly those low in inflammatory foods, are associated with a lower risk of depression.

Reference: Lassale C, Batty GD, Baghdadli A, et al. Healthy dietary indices and risk of depressive outcomes: a systematic review and meta-analysis of observational studies. Mol Psychiatry. 2019 Jul;24(7):965-986. doi: 10.1038/s41380-018-0237-8. Erratum in: Mol Psychiatry. 2018;: Erratum in: Mol Psychiatry. 2021;26(7):3657.