Background & aims: The relationship between diet, inflammation and mental health is of increasing interest. However, limited data regarding the role of dietary inflammatory potential in this context exist. Therefore the aim of this work was to examine associations between the inflammatory potential of habitual diet and mental health outcomes in a cross-sectional sample of 2047 adults (50.8% female).

Methods: Diet was assessed using a self-completed food frequency questionnaire from which dietary inflammatory index (DII^®) scores were determined. Depressive symptoms, anxiety and well-being were assessed using the CES-D, HADS-A and WHO-5 screening tools.

Results: Logistic regression analyses revealed that higher energy-adjusted DII (E-DII^®) scores, reflecting a more pro-inflammatory diet, were associated with increased risk of depressive symptoms (odds ratios (OR) 1.70, 95% confidence intervals (CI) 1.23-2.35, p = 0.001) and anxiety (OR 1.60, 95% CI 1.15-2.24, p = 0.006) and lower likelihood of well-being (OR 0.62, 95% CI 0.46-0.83, p = 0.001), comparing highest to lowest tertile of E-DII. In gender-stratified analyses associations were noted in women only. Women with the highest E-DII scores were at elevated risk of depressive symptoms (OR 2.29, 95% CI 1.49-3.51, p < 0.001) and anxiety (OR 2.00, 95% CI 1.30-3.06, p = 0.002), while likelihood of reporting good well-being was lower (OR 0.55, 95% CI 0.36-0.79, p = 0.002), relative to those with the lowest E-DII scores.

Conclusions: These findings, which suggest that a pro-inflammatory diet is associated with adverse mental health, may be of clinical and public health significance regarding the development of novel nutritional psychiatry approaches to promote good mental health.