Objective: The aim of this study is to identify the changes on brain magnetic resonance imaging in patients suffering from depressive disorders.
Methodology: Data and findings were taken from previous studies that have been covering brain changes demonstrated on serial magnetic resonance imaging among individuals diagnosed with major depressive disorder.
Results: Reductions in the size of the hippocampus, basal ganglia, orbital frontal cortex, prefrontal cortex, putamen, caudate nucleus, amygdala, anterior and posterior cingulate, insula and temporal lobes whereas lateral ventricles enlarged.
Conclusion: Patients suffering from depressive disorders demonstrate significant brain changes that are apparent on magnetic resonance imaging scan but it's unknown whether these changes are causes or consequences of depressive illness.
Major Depressive Disorder; Brain Magnetic Resonance Imaging; Hippocampus; Orbital Frontal Cortex
Major depressive disorder (MDD) is a serious mental disorder that is characterized by at minimum one depressive episode lasting for at least 2 weeks and involving changes in mood, pleasure, interests, cognitive symptoms and vegetative symptoms. The symptoms that characterize major depressive episode and major depressive disorder overlap with depressive symptoms among bipolar disorder and schizophrenic patients; that is the reason why the application of exclusion criteria enables diagnosis of MDD [1].
Studies estimate that around 10% to 15% of population will experience clinically significant depressive symptoms during their lifetime, and around 9% of women and about 5% of men will experience symptoms of depressive disorder according to World Health Organization (WHO). Twin, adoption and family studies indicated that genetics play important roles in development of MDD. Twin studies suggest heritability of around 40 - 50%, and family studies demonstrate two to three folds increase in lifetime risk of developing depressive disorder among first-degree relatives [2].
Many studies have shown that a major depressive episode is characterised by typical neuroendocrine and sleep-EEG alterations. Over activity of the hypothalamic pituitary (HPA) axis, a key neuroendocrine alteration observed in patients suffering from an acute major depressive episode, is assumed to reflect an elevation of hypothalamic corticotropin-releasing hormone (CRH) and vasopressin secretion [3].
Symptoms of depression, minor depression, persistent depressive disorders (dysthymic disorder) and major depressive disorder represent a continuum of depressive symptom severity in unipolar depressive disorder, in which each level is associated with significant stepwise impairment and deterioration in psychosocial disability [4].
Beside mental and somatic symptoms, depressive disordered patients have brain changes that can be readily seen in brain imaging scans, thus this study aimed at identifying the changes on brain magnetic resonance imaging (MRI) in patients suffering from depressive disorders since this issue has not been extensively studied in literature.
Data and findings were taken from previous studies that have been covering brain changes demonstrated on serial MRI scans among individuals diagnosed with major depressive disorder.
Significant brain changes on MRI were documented in such patients and have been recorded and summarized in a short paper.
Findings from this study showed that there are consistent reductions in the size of the hippocampus, basal ganglia, orbital frontal cortex and subgenual prefrontal cortex in MDD patients [5].
Specific changes include lower gray matter volumes in amygdala, dorsal frontomedian cortex, and right paracingulate cortex [6].
Moreover, patients showed large reductions in the size of frontal regions, particularly in anterior cingulate and orbitofrontal cortex and showed smaller reductions in prefrontal cortex whereas hippocampus, caudate nucleus and putamen showed moderate reductions in volume [7].
In addition, another paper found that depressed individuals had significantly lower hippocampal volumes, smaller amygdala, larger lateral ventricles, and larger caudate volumes [8].
Furthermore, adults having MDD had thin cortical gray matter in orbitofrontal cortex, insula, anterior and posterior cingulate, and in the temporal lobes. On the other hand, adolescents showed smaller total surface area and frontal lobes regional reductions (superior frontal gyrus and medial orbitofrontal cortex) and higher-order somatosensory, visual and motor areas (9).
It's important to request an MRI of the brain in every patient presenting with prominent symptoms of depression particularly if it's for long duration, to rule out specific neurological aetiology of depressive illness as cerebrovascular disease, brain tumours in frontal lobes and multiple sclerosis.
Although above neurological diseases are frequently associated with depressive psychopathology, clinically it's difficult to determine whether these neurological diseases resulted in depression or both of them simultaneously present. Clues for differentiation probably can be helped by knowing the chronology and the predominance of symptoms.
This study concluded that patients suffering from depressive disorders demonstrate significant brain changes that are apparent on MRI scan. The relationship between brain changes and depressive disorders are complex and yet not fully understood. It's still unknown that whether these brain abnormalities are actually causes or consequences of depression, and thus more study is needed to discuss this dilemma.
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- Sacher J, Neumann J, Fünfstück T, Soliman A, Villringer A, Schroeter ML. (2012) Mapping the depressed brain: A meta-analysis of structural and functional alterations in major depressive disorder. Journal of Affective Disorders 140: 8-142. [Crossref]
- Koolschijn PCMP, van Haren NEM, Lensvelt-Mulders GJLM, Hulshoff Pol HE, Kahn RS. (2009) Brain volume abnormalities in major depressive disorder: A meta-analysis of magnetic resonance imaging studies. Hum Brain Mapp 30: 35-3719. [Crossref]
- Schmaal L, Veltman DJ, van Erp TGM, Sämann PG, Frodl T, et al. (2016) Subcortical brain alterations in major depressive disorder: findings from the ENIGMA Major Depressive Disorder working group. Mol Psychiatry 21: 12-806. [Crossref]
- Schmaal L, Hibar DP, Sämann PG, Hall GB, Baune BT, et al. (2017) Cortical abnormalities in adults and adolescents with major depression based on brain scans from 20 cohorts worldwide in the ENIGMA Major Depressive Disorder Working Group. Mol Psychiatry 22: 9-900. [Crossref]
