Association Between Vitamin D Levels and Severity of Depressive Symptoms: An Observational Study.

Abstract

Background: Depression is a leading cause of disability worldwide, and vitamin D deficiency has emerged as a potential modifiable risk factor [1,2]. India bears a substantial burden of both conditions, yet data from South India remain limited. Aim: To determine the association between serum 25-hydroxyvitamin D [25(OH)D] levels and the severity of depressive symptoms among patients attending a care hospital in South India. Methods: This observational cross-sectional study was conducted over nine months (April–December 2025) among 50 adults diagnosed with depressive disorders. Serum 25(OH)D was measured, and depression severity was assessed using the Patient Health Questionnaire-9 (PHQ-9). Correlation and regression analyses were performed. Results: The mean serum 25(OH)D level was 18.6 ± 7.2 ng/mL; 74% of participants were vitamin D deficient (<20 ng/mL). A statistically significant inverse correlation was observed between 25(OH)D levels and PHQ-9 scores (r = −0.51, p < 0.001). Participants with severe depression had significantly lower 25(OH)D levels (12.4 ± 4.1 ng/mL) compared to those with mild depression (24.8 ± 6.3 ng/mL; p < 0.001). Conclusion: Vitamin D deficiency is highly prevalent among depressed patients in South India and is significantly associated with greater depressive symptom severity [4-6]. Routine screening and correction of vitamin D deficiency may be warranted in this population.