Structural and Functional Neuroimaging in Major Depressive Disorder with Suicidal Ideation: A Review

Major depressive disorder with suicidal ideation (MDD-SI) represents a clinically high-risk subtype of depressive disorders characterized by marked neurobiological heterogeneity and has become a major focus of suicide prevention and precision intervention research. In recent years, neuroimaging studies have increasingly demonstrated that patients with MDD-SI exhibit distinct structural and functional brain alterations compared with depressed patients without suicidal ideation. These abnormalities primarily involve the prefrontal–cingulate–limbic system, the default mode network (DMN), and reward-related circuits. With the growing number of longitudinal neuroimaging studies, accumulating evidence suggests that biological treatments—particularly electroconvulsive therapy (ECT)—not only lead to significant reductions in depressive symptoms and suicidal ideation but also induce measurable structural and functional plasticity in these key brain regions and networks. Structural MRI studies indicate that, at baseline, patients with MDD-SI commonly show gray matter abnormalities in regions such as the anterior cingulate cortex, prefrontal cortex, and hippocampus. Following ECT treatment, regionally selective structural changes have been observed, most notably hippocampal volume increases and structural recovery in the anterior cingulate cortex and ventromedial prefrontal cortex. Functional neuroimaging studies further demonstrate that treatment-related reductions in suicidal ideation are accompanied by enhanced prefrontal–limbic regulatory control, normalization of anterior cingulate cortex function, and suppression of excessive self-referential processing within the DMN. Collectively, these findings suggest that treatment-related neuroimaging changes may constitute an important neural substrate underlying the improvement of suicidal ideation. This review summarizes current structural and functional neuroimaging findings in patients with MDD-SI before and after treatment, with particular emphasis on treatment-related plasticity in key brain regions and networks. Furthermore, an integrative conceptual framework—linking baseline structural abnormalities, treatment-induced neuroplasticity, and the alleviation of suicidal ideation—is proposed to provide insights for future research on imaging-based predictive biomarkers and the neurobiological mechanisms underlying treatment response.