The role of the Mediterranean dietary pattern in the management of depression among adults: A systematic review and meta-analysis of randomized controlled trials

Background: Depression is one of the leading causes of disability and disease burden worldwide, and a substantial gap exists between the global need for mental health care and its provision. Nutritional interventions, such as the Mediterranean diet (MD), have been proposed as accessible, cost-effective adjuncts or alternatives to conventional depression therapies, yet randomised evidence specifically evaluating the whole MD pattern remains scarce.
Aim: To determine the effectiveness of the MD in reducing depressive symptoms among adults globally, and to examine whether this effectiveness varies according to geographical setting.
Methods: A systematic review and meta-analysis of randomised controlled trials (RCTs) was conducted in accordance with the PRISMA 2020 guidelines and a registered PROSPERO protocol. Five databases (MEDLINE, CINAHL, APA PsycInfo, Embase and Scopus) were searched without date restriction owing to the sparsity of relevant RCTs. Methodological quality was appraised using the Cochrane Risk of Bias tool (RoB 2.0). Standardised mean differences (SMD) with standard errors were pooled using a random-effects model in Review Manager 5.4.1.
Results: Seven RCTs (764 randomised participants, 683 completers) met the eligibility criteria; five (438 participants) were pooled in the meta-analysis. Only one study had an overall low risk of bias, while three had some concerns and three had a high risk of bias. The pooled analysis showed a significant improvement in depressive symptoms favouring the MD (SMD = 0.50, 95% CI 0.09–0.90, p = 0.02), with no evidence of statistical heterogeneity (I² = 0%, Chi² = 0.06, p = 1.00). The effect remained significant after excluding the single high-risk-of-bias study, but became non-significant (p = 0.58) after removing the most heavily weighted trial. Subgroup analysis by geographical setting could not be performed, as all five pooled trials originated from Australia.
Conclusion: There is encouraging, but fragile, evidence that the MD reduces depressive symptoms in adults. The diversity of depressive symptom measurement tools, small sample sizes, short trial durations, and the geographical concentration of the available evidence in a single country limit the strength and generalisability of these conclusions.
Implications for public health and health promotion: Further well-powered, methodologically robust RCTs across diverse geographical and cultural settings, using standardised outcome measures and explicit behaviour-change frameworks, are required before the MD can be confidently recommended within public health nutrition policy for the management of depression.