Relationship Between Vitamin D Status, Neurocognitive Function, and Depressive Symptom Severity in Patients with Major Depressive Disorder

Abstract

Background: Major depressive disorder is frequently accompanied by cognitive difficulties that may impair daily functioning and treatment outcomes. The role of vitamin D in brain function, mood regulation and the performance of the neurocognitive function has been more and more investigated. The purpose of this study was to determine whether there was a correlation between depression severity, vitamin D status and neurocognitive function in patients with major depression.

Methods: This cross-sectional analytical study was conducted at Khalifa Gul Nawaz Teaching Hospital, Bannu from January 2025 to June 2025. The subjects were selected by non-probability consecutive sampling technique, total of 78 patients with major depressive disorder were selected. Serum 25-hydroxyvitamin D (25(OH)D) was quantified, and vitamin D deficiency, insufficiency, or sufficiency was defined. The Montreal Cognitive Assessment (MoCA) was used to measure neurocognitive function and the Patient Health Questionnaire-9 (PHQ-9) was used to measure the severity of depressive symptoms. IBM SPSS Statistics version 25.0 was used for data analysis. The group comparisons were performed by using group correlation, chi-square testing and a p value <0.05 was accepted as statistically significant.

Results: The mean serum vitamin D level was 21.7 ± 9.4 ng/mL. Vitamin D deficiency was present in 35 (44.9%) participants, insufficiency in 25 (32.1%), and sufficient levels in 18 (23.1%). The mean MoCA score increased significantly across deficient, insufficient, and sufficient vitamin D groups (20.8 ± 3.9, 23.5 ± 3.4, and 26.2 ± 3.1, respectively; p < 0.001). Mean PHQ-9 scores showed the opposite pattern (18.4 ± 4.7, 15.0 ± 4.2, and 11.8 ± 4.0, respectively; p < 0.001). Cognitive impairment was significantly more frequent among vitamin D-deficient patients (71.4%) than among those with insufficient (48.0%) or sufficient (27.8%) vitamin D levels (p = 0.005). Serum vitamin D was positively correlated with MoCA score (r = 0.52, p < 0.001) and inversely correlated with PHQ-9 score (r = −0.47, p < 0.001).

Conclusion: Lower vitamin D levels were significantly associated with poorer neurocognitive performance and greater depressive symptom severity among patients with major depressive disorder. Assessment of vitamin D status may provide useful supplementary information in the evaluation of patients with MDD, although larger longitudinal and interventional studies are required to determine causality.