The Effect Of Serum Vitamin D On Major Depressive Disorder And Its Possible Neural Basis

Background: Depression has been linked to vitamin D deficiency.However,little attention was paid to the neural substrate underlying this association.Methods: Fifty patients with major depressive disorder(MDD)and thirty-six genderand age-matched healthy controls(HC)underwent structural and diffusion tensor magnetic resonance imaging(MRI).High-resolution structural magnetic resonance imaging was performed to calculate total intracranial volume(TIV).Voxel-based morphometry(VBM)and tract-based spatial statistics(TBSS)analyses were performed to assess gray matter structure and white matter integrity,respectively.Peripheral venous blood samples were collected to measure serum vitamin D concentration.Hamilton Rating Scale for Depression(HAMD)was used to assess severity of depression symptoms.In the MDD patients,the relationship among brain imaging parameters,serum vitamin D concentration,and HAMD score was examined using correlation,linear regression,and mediation analyses.Results: Compared with healthy controls,the TIV in patients with MDD is great decreased(t =-1.990,P = 0.050)but no significant difference was found in gray matter volume(GMV)and white matter integrity(FA).In patients with MDD,HAMD score was negatively correlated with TIV and serum vitamin D concentration,and TIV was positively correlated with serum vitamin D concentration.Linear regression analyses showed that TIV and serum vitamin D concentration were significant predictors of HAMD score.Importantly,mediation analysis revealed that TIV significantly mediated the relationship between serum vitamin D concentration and HAMD score.However,there were no significant correlations between other brain imaging parameters(i.e.GMV and FA)and HAMD score as well as serum vitamin D concentration.Conclusion: Our findings suggest that TIV may serve as a potential neural biomarker for monitoring responses to adjuvant therapy of vitamin D in patients with MDD.