Brain structure alterations in depression: Psychoradiological evidence

Abstract

Depression is the leading cause of disability around the world, but little is known about its pathology. Currently, the diagnosis of depression is made based on clinical manifestations, with little objective evidence. Magnetic resonance imaging (MRI) has been used to investigate the pathological changes in brain anatomy associated with this disorder. MRI can identify structural alterations in depressive patients in vivo, which could make considerable contributions to clinical diagnosis and treatment. Numerous studies that focused on gray and white matter have found significant brain region alterations in major depressive disorder patients, such as in the frontal lobe, hippocampus, temporal lobe, thalamus, striatum, and amygdala. The results are inconsistent and controversial because of the different demographic and clinical characteristics. However, some regions overlapped; thus, we think that there may be a "hub" in MDD and that an impairment in these regions contributes to disease severity. Brain connections contain both structural connections and functional connections, which reflect disease from a different view and support that MDD may be caused by the interaction of multiple brain regions. According to previous reports, significant circuits include the frontal-subcortical circuit, the suicide circuit, and the reward circuit. As has been recognized, the pathophysiology of major depressive disorder is complex and changeable. The current review focuses on the significant alterations in the gray and white matter of patients with the depressive disorder to generate a better understanding of the circuits. Moreover, identifying the nuances of depressive disorder and finding a biomarker will make a significant contribution to the guidance of clinical diagnosis and treatment.

No Alterations of Brain Structural Asymmetry in Major Depressive Disorder: An ENIGMA Consortium Analysis

“…Much of the neurobiology of major depression is unknown, but subtle alterations of brain structure may be involved, and various MRI-based studies have observed regional brain differences between individuals with major depression and healthy control subjects. A recent review of the literature by Zhang et al (4) described various possible structural alterations in the brains of individuals with major depression, such as case-control differences in the thickness of the medial orbitofrontal cortex and inferior parietal gyrus. However, it was also noted that the results of structural MRI studies in major depression have often been inconsistent (4).…”

“…A recent review of the literature by Zhang et al (4) described various possible structural alterations in the brains of individuals with major depression, such as case-control differences in the thickness of the medial orbitofrontal cortex and inferior parietal gyrus. However, it was also noted that the results of structural MRI studies in major depression have often been inconsistent (4). This inconsistency is likely due to the use of small study sample sizes in relation to subtle effects, as well as heterogeneity among studies in terms of clinical characteristics and methodology; for example, hardware and software differences between scanners and distinct data processing pipelines can contribute to heterogeneity (5).…”

“…Some of the average brain anatomical differences between individuals with major depression and control subjects, described in the review by Zhang et al (4), involved only one of the two hemispheres. Zhang et al concluded that the right medial orbitofrontal cortex was often found to be thinner, and the volumes of the left middle frontal gyrus and the right thalamus lower, in individuals with major depression than in control subjects (4).…”

“…Some of the average brain anatomical differences between individuals with major depression and control subjects, described in the review by Zhang et al (4), involved only one of the two hemispheres. Zhang et al concluded that the right medial orbitofrontal cortex was often found to be thinner, and the volumes of the left middle frontal gyrus and the right thalamus lower, in individuals with major depression than in control subjects (4). The ENIGMA consortium study of the cerebral cortex found that the thickness of the inferior temporal gyrus and caudal anterior cingulate was significantly thinner in adults with major depression only on the right side, but not on the left (7).…”

Imaging connectomics in depression

“…We assembled four review articles. In the first review article, Zhang et al systematically reviewed recent neuroimaging studies regarding significant structural alterations in brain regions and circuits in patients with major depressive disorder (MDD). They highlighted regional gray matter (GM) changes in several crucial regions in MDD, including the frontal lobe (mainly parts of the anterior cingulate, orbitofrontal, and dorsolateral prefrontal cortices), the thalamus, the striatum, the parietal lobe, and the hippocampus.…”