Abstract
Previous structural imaging studies have found evidence of brain morphometric changes in patients with major depressive disorder (MDD), but these studies rarely excluded compounding effects of certain important factors, such as medications and long duration of illnesses. Furthermore, the neurobiological mechanism of the macroscopic findings of structural alterations in MDD patients remains unclear. In this study, we utilized magnetization transfer imaging, a quantitative measure of the macromolecular structural integrity of brain tissue, to identify biophysical alterations, which are represented by a magnetization transfer ratio (MTR), in MDD patients. To ascertain whether MTR changes occur independent of volume loss, we also conduct voxel-based morphometry (VBM) analysis. The participants included 27 first-episode, drug-naive MDD patients and 28 healthy controls matched for age and gender. Whole-brain voxel-based analysis was used to compare MTR and gray matter volume across groups and to analyse correlations between MTR and age, symptom severity, and illness duration. The patients exhibited significantly lower MTR in the left superior parietal lobule and left middle occipital gyrus compared with healthy controls, which may be related to the attentional and cognitive dysfunction in MDD patients. The VBM analysis revealed significantly increased gray matter volume in right postcentral gyrus in MDD patients. These findings in first-episode, drug-naive MDD patients may reflect microstructural gray matter changes in the parietal and occipital cortices close to illness onset that existed before volume loss, and thus potentially provide important new insight into the early neurobiology of depression.
Highlights
As one of the leading worldwide causes of disability, major depressive disorder (MDD) is characterized by persistent, pervasive feelings of sadness, guilt and worthlessness, and often results in an increased risk of suicide.1 MDD causes significant individual suffering and impairs social and occupational functioning, resulting in a major public health and economic burden
No association was found between regional magnetization transfer ratio (MTR) values and patient age, Hamilton Rating Scale for Depression (HRSD) scores or illness durations (P = 0.391 for age and left superior parietal lobule (SPL); P = 0.05 and P = 0.985 for age and two left middle occipital gyrus (MOG) regions; P = 0.073 for HRSD scores and left SPL; P = 0.424 and P = 0.507 for HRSD scores and two left MOG regions, respectively; P = 0.143 for illness duration and left SPL; P = 0.319 and P = 0.8 for illness duration and two left MOG regions, respectively)
In the present study, we used Magnetization transfer imaging (MTI) to explore the microstructural changes in first-episode, drug-naive MDD patients relative to healthy controls
Summary
As one of the leading worldwide causes of disability, major depressive disorder (MDD) is characterized by persistent, pervasive feelings of sadness, guilt and worthlessness, and often results in an increased risk of suicide. MDD causes significant individual suffering and impairs social and occupational functioning, resulting in a major public health and economic burden. As one of the leading worldwide causes of disability, major depressive disorder (MDD) is characterized by persistent, pervasive feelings of sadness, guilt and worthlessness, and often results in an increased risk of suicide.. Larger volumes of white matter in the inferior parietal lobule and periventricular regions and deep or subcortical white matter hyperintensity have been reported. These reports are inconsistent in detail, probably because of potential confounders associated with medications and/or long duration of illnesses. Studies of first-episode, drug-naive MDD are a starting point for assessing brain structure before it is influenced by potential confounders and thereby provide core information relevant to models of pathogenesis.
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