Dietary patterns and depression: a comprehensive review of associations, moderating factors, and underlying mechanisms

Depression is a widespread and multifaceted mental health disorder, shaped by genetic susceptibility, neurobiological dysfunction, and environmental stressors, which pose challenges for effective treatment. Emerging evidence suggests that diet plays a significant role in the occurrence and progression of depression, and depressive symptoms themselves may in turn influence eating behavior. In this narrative review, we examined the dual beneficial and harmful effects of dietary patterns on depression. We searched PubMed and Web of Science from January 2000 to March 2026 and synthesized evidence from about 200 relevant publications to identify peer-reviewed observational studies and randomized controlled trials (RCT) that evaluated the association between overall dietary patterns and depressive outcomes in people of different age groups. Our synthesis showed that healthy dietary patterns, such as the Mediterranean Diet (MD), the Nordic Diet (ND), the Japanese Diet (JD), the Dietary Approaches to Stop Hypertension (DASH), and the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND), have been linked to a reduction in depressive symptoms, primarily due to their anti-inflammatory and antioxidant effects. In contrast, unhealthy dietary patterns rich in processed foods, saturated fats, and refined sugars appear to worsen depression by promoting systemic inflammation and impairing metabolic function. We also explored the biological mechanisms mediating these effects, including alterations in gut microbiota, oxidative stress, and neuroinflammation. Additionally, we discuss how individual factors - such as age, sex, genetic background, and disease severity may influence the efficacy of dietary interventions. In summary, healthy dietary patterns are associated with reduced depressive symptoms, whereas the Western diet(WD) is linked to increased depression risk, with these associations modulated by age, sex, socioeconomic status, and disease severity, supporting the need for personalized nutritional approaches.