Nutrition and Mental Health in Endocrine Disorders with a Focus on Depression and Depressive Symptoms: A Systematic Review

Background: Endocrine disorders, including diabetes, thyroid dysfunction, and polycystic ovary syndrome (PCOS), are associated with an increased risk of depression and reduced quality of life. Recent evidence has highlighted the role of nutrition and dietary patterns in improving mental health outcomes in these patients. Methods: This systematic review was conducted in accordance with the PRISMA 2020 guidelines. A comprehensive search was performed in PubMed, Scopus, Web of Science, and Google Scholar up to September 2025. Both interventional and observational studies evaluating the effects of nutritional factors on depression among patients with endocrine disorders were included. Study quality was assessed using the Revised Cochrane risk-of-bias tool for randomized trials (ROB2) and Joanna Briggs Institute critical appraisal tools (JBI) tools. Results: Of 832 studies initially identified, 38 met the eligibility criteria (15 interventional, 23 observational). Four randomized clinical trials and one review demonstrated that vitamin D supplementation was associated with reductions in depressive symptoms among patients with diabetes and PCOS. Six observational studies reported that higher dietary quality, adherence to healthy dietary patterns, and higher intakes of flavonoids and plant-based proteins were linked to lower depressive symptoms in type 1 and type 2 diabetes. In contrast, consumption of ultra-processed foods and food insecurity were associated with a higher risk of depression in type 2 diabetes. Evidence regarding omega-3 fatty acids remained inconsistent. Conclusion: The findings of this review suggest that nutrition and healthy dietary patterns may play an important role in improving mental health in patients with endocrine disorders. However, heterogeneity across studies and the limited evidence available for thyroid disorders underscore the need for larger, well-designed clinical trials.