Summary:
Depression and anxiety are among the leading contributors to the global burden of disease, affecting daily functioning, quality of life, and in some cases leading to self-harm. Current treatments, including medication and cognitive therapies, can be effective but are often limited by high relapse rates and unstable long-term outcomes, creating a need for new strategies. Increasing evidence suggests that diet may influence mental health through its impact on systemic inflammation, a mechanism thought to play a role in the development of mood disorders. The Dietary Inflammatory Index (DII) was developed to measure the inflammatory potential of overall dietary patterns. Unlike approaches that examine individual foods or nutrients, the DII provides a score where higher values indicate pro-inflammatory diets and lower scores reflect anti-inflammatory diets. This index has been used to investigate links between diet, chronic disease, and mental health, with emerging studies reporting associations between higher DII scores and increased risk of depression and anxiety. This paper is a systematic review and meta-analysis, conducted using data from 43 studies. Analysis showed that higher DII scores were significantly associated with an increased risk of depression. Further analyses across variables such as age, gender, region, and body mass index consistently supported this association. Risk of depression also rose progressively with higher, pro-inflammatory scores. Overall, these findings suggest that pro-inflammatory diets may increase vulnerability to depression, and possibly anxiety, while anti-inflammatory dietary patterns may be protective. The results support the value of dietary interventions aimed at lowering dietary inflammation as part of strategies to prevent or reduce the burden of mood disorders.
Abstract:
Background: Depression is a prevalent mental health disorders that impose a significant global health burden. Emerging evidence suggests that diet plays a critical role in mental health, primarily through its impact on inflammation. The Dietary Inflammatory Index (DII) is a validated tool designed to assess the inflammatory potential of an individual’s diet. Objective: To systematically evaluate the association between DII and the risk of depression. Methods: A comprehensive search was conducted in PubMed, Cochrane Library, Embase, and Web of Science from inception to August 9, 2025. Two independent reviewers screened the studies, extracted data, and assessed methodological quality. A meta-analysis was performed to evaluate the association between DII and depression (the main outcome). The dose–response relationship between DII and depression was further analyzed using generalized least squares estimation and restricted cubic spline models in Stata 18.0. Results: A total of 43 studies were included. The meta-analysis revealed that higher DII scores were associated with an increased risk of depression (OR = 1.53; 95% CI: 1.42 to 1.66; I2 = 81.5%). Subgroup analyses stratified by study design, gender, age, region, dietary assessment methods, depression assessment tools, and body mass index (BMI) consistently showed a positive association between higher DII and depression risk. Dose–response analysis indicated a nonlinear relationship (p = 0.0019): no significant association was observed for DII scores below 0, whereas the risk increased progressively for scores above 0. Exploratory analyses of a smaller subset of studies suggested a similar trend for anxiety, but this finding should be interpreted with caution. Conclusion: Higher DII scores are associated with an increased risk of depression. These results highlight the potential benefits of reducing pro-inflammatory dietary components and encouraging anti-inflammatory eating patterns to support mental health, particularly in the prevention of depression.
Article Publication Date: 12/09/2025
DOI: 10.3389/fnut.2025.1645789
