Dietary n-3 PUFA, fish consumption and depression: A systematic review and meta-analysis of observational studies

Background Fish consumption and n-3 polyunsaturated fatty acids (PUFA) have been hypothesized to exert preventive effects toward depressive disorders, but findings are contrasting. We aimed to systematically review and perform meta-analysis of results from observational studies exploring the association between fish, n-3 PUFA dietary intake, and depression. Methods A search on the main bibliographic source of the observational studies up to August 2015 was performed. Random-effects models of the highest versus the lowest (reference) category of exposure and dose-response meta-analysis were performed. Results A total of 31 studies including 255,076 individuals and over 20,000 cases of depression, were examined. Analysis of 21 datasets investigating relation between fish consumption and depression resulted in significant reduced risk (RR=0.78, 95% CI: 0.69, 0.89), with a linear dose-response despite with moderate heterogeneity. Pooled risk estimates of depression for extreme categories of both total n-3 PUFA and fish-derived n-3 PUFA [eicosapentaenoic acid (EPA)+docosahexaenoic acid (DHA)] resulted in decreased risk for the highest compared with the lowest intake (RR=0.78, 95% CI: 0.67, 0.92 and RR=0.82, 95% CI: 0.73, 0.92, respectively) and dose-response analysis revealed a J-shaped association with a peak decreased risk for 1.8 g/d intake of n-3 PUFA (RR=0.30, 95% CI: 0.09, 0.98). Limitation Design of the studies included and confounding due to lack adjustment for certain variables may exist. Conclusions The present analysis supports the hypothesis that dietary n-3 PUFA intake are associated with lower risk of depression.