A Volumetric-Metabolic Study Of Hippocampal Alteration In Female Major Depressive Disorder Patients

Background: Major depressive disorder(MDD)is one of the most frequently diagnosed mental disorders in the world today and poses a higher risk in women(roughly double)than in men.Despite this,there is a lack of substantial knowledge about both the underpinnings of MDD and the physiomorphological consequences it might bring to anatomical brain regions.There are some clinical reports suggesting hippocampal shrinkage in patients with MDD,while there also exist other studies that,in contrary,have failed to find this hippocampal variation when comparing MDD patients with healthy subjects.The mechanisms underlying MDD,especially the gender-related difference in hippocampal volumetric-metabolic alteration of MDD patients,remain not fully understood.This study aimed to investigate the hippocampal morphometry and metabolite concentration alteration in female MDD patients compared to healthy controls.Methods: In this study 27 female individuals were recruited,in which 15 were MDD subjects and 12 were healthy controls.The data used was acquired using a 3.0T Siemens Verio MRI scanner at the Shanghai Mental Health Center,China.The morphometric analysis was performed by employing two different magnet resonance imaging analysis approaches by using the following software: Voxel Based Morphometry(VBM)toolbox and Free Surfer.Furthermore,the left and right hippocampal volumetric results achieved from these mentioned software were analyzed in units of hippocampal absolute volume(H-AV)and hippocampal grey and white matter volumes(H-GMV and H-WMV,respectively).The statistical comparisons were further performed on both the following packages: Statistical Parametric Mapping(SPM)and Statistical Package for the Social Science(SPSS).The analysis of metabolic concentration was done using LCModel software and the followed hippocampal volumetric-metabolic correlation investigation was performed using SPSS.Results: In the volumetric study no significant volumetric differences were found between female MDD patients and healthy controls.On the other hand,in the metabolite concentration alteration study a significant positive correlation(R = 0.576,p= 0.05)between the right hippocampal absolute volume and its metabolite Choline(Cho)concentration was found.Conclusion: Our results showed that the hippocampus did not adopt a morphological change in female MDD patients.Regarding other studies showing the opposite,we can not entirely discard the possibility that the hippocampus may change as an effect of MDD.This volumetric change might be related to several factors such as the time taken for onset of the disease,recurrence and periodicity of depression,in which gender may also played an important role.The positive correlation between right hippocampus absolute volume and Cho concentration showed an association of neurodegradation or cellular membrane turnover with the structural alteration of hippocampus in female MDD patients.To our knowledge,this is the first findings of a volumetric-metabolic correlation of the hippocampus alteration in female MDD study.The detailed underpinnings of female MDD anatomical and metabolic variations merit further investigations.