Serum Vitamin B12 Status and Its Association with Depression Severity in Newly Diagnosed Patients: A Hospital-Based Cross-Sectional Study from Central India

Background: Vitamin B12 deficiency is increasingly recognized as a modifiable biochemical contributor to depressive illness, particularly in Indian populations with high rates of vegetarianism. However, data on the relationship between serum B12 levels and depression severity from central India remain limited.

Objectives: To determine the prevalence of serum Vitamin B12 deficiency in newly diagnosed depression patients and to assess its association with depression severity using dual validated instruments — the Patient Health Questionnaire-9 (PHQ-9) and Beck's Depression Inventory (BDI).

Methods: A hospital-based, observational cross-sectional study was conducted at Gandhi Medical College and Hamidia Hospital, Bhopal, over 18 months. A total of 114 newly diagnosed depression patients (DSM-5 criteria), aged 18–60 years, were enrolled. Serum Vitamin B12 was estimated by Chemiluminescent Immunoassay (CLIA) on a Beckman Coulter DXI 800 analyzer. Depression severity was assessed using PHQ-9 and BDI. Non-parametric statistical tests (Kruskal-Wallis, Mann-Whitney U, Spearman's rank correlation) were applied throughout, given non-normal data distribution confirmed by Shapiro-Wilk testing.

Results: Vitamin B12 deficiency (<200 pg/mL) was found in 61.4% of participants, with 82.5% showing suboptimal levels overall. The overall median serum B12 was 156.72 pg/mL (IQR: 150.33). Although Kruskal-Wallis analysis showed no statistically significant difference across PHQ-9 (H = 5.528, p = 0.137) or BDI (H = 4.691, p = 0.196) severity categories, a clinically meaningful declining trend was observed: BDI-Mild (188.51 pg/mL), Moderate (148.44 pg/mL), and Severe (110.75 pg/mL). Spearman's correlation of B12 with PHQ-9 (r = −0.169, p = 0.073) and BDI (r = −0.172, p = 0.067) approached but did not reach significance. Males had significantly lower B12 levels than females (135.21 vs. 213.40 pg/mL; U = 2042.00, p = 0.017).

Conclusion: Vitamin B12 deficiency is endemic among newly diagnosed depression patients in central India. Although a statistically significant association with depression severity was not established, a consistent and clinically meaningful inverse trend was demonstrated, approaching significance on both assessment scales. Routine B12 screening in all newly diagnosed depression patients is warranted. Larger prospective studies with control groups are recommended to confirm causality.