Coffee, tea, caffeine and risk of depression: A systematic review and dose–response meta‐analysis of observational studies

Scope The aim of the study was to systematically review and analyze results from observational studies on coffee, caffeine, and tea consumption and association or risk of depression. Methods and results Embase and PubMed databases were searched from inception to June 2015 for observational studies reporting the odds ratios or relative risks (RRs) and 95% confidence intervals (CI) of depression by coffee/tea/caffeine consumption. Random effects models, subgroup analyses, and dose–response analyses were performed. Twelve studies with 23 datasets were included in the meta‐analysis, accounting for a total of 346 913 individuals and 8146 cases of depression. Compared to individuals with lower coffee consumption, those with higher intakes had pooled RR of depression of 0.76 (95% CI: 0.64, 0.91). Dose–response effect suggests a nonlinear J‐shaped relation between coffee consumption and risk of depression with a peak of protective effect for 400 mL/day. A borderline nonsignificant association between tea consumption and risk of depression was found (RR 0.70, 95% CI: 0.48, 1.01), while significant results were found only for analysis of prospective studies regarding caffeine consumption (RR = 0.84, 95% CI: 0.75, 0.93). Conclusion This study suggests a protective effect of coffee and, partially, of tea and caffeine on risk of depression.