Pharmacological treatment-associated brain structural and functional alterations in major depressive disorder: A narrative review

Abstract

Major depressive disorder (MDD) is a complicated mental disorder with an unclear etiology and a relatively limited response to treatment. Magnetic resonance imaging (MRI) can help identify the underlying neuropathophysiological mechanisms of MDD. A better understanding of structural and functional alterations in the brain before and after treatment is necessary to improve treatment targets at the brain level. This narrative review summarizes the literature on longitudinal MRI studies in MDD, which identify brain regions with changes in neural activity after antidepressant treatment, providing an objective imaging basis for early diagnosis and assessment of the efficacy of antidepressant therapy. It was found that the neural activity in the prefrontal cortex, cingulate cortex, precuneus, and hippocampus was reduced in patients with untreated MDD. In addition, functional connectivity of the default mode network (DMN), central executive, and salience networks was enhanced, gray matter volume was reduced, and white matter structure was damaged. After antidepressant treatment, neural activity in some brain regions increased and functional connectivity of brain networks and gray and white matter structures returned to normal states. Although the results have been inconsistent, amygdala hypoactivation and anterior cingulate cortex hyperactivation in response to negative emotional stimuli are promising predictors of successful treatment, and hyperconnectivity within and between the DMN and executive control network exhibit similar results.