Neuroimaging Correlates of Depression after Traumatic Brain Injury: A Systematic Review.

Depression is the most frequent neuropsychiatric complication after traumatic brain injury (TBI) and is associated with poorer outcomes. Neuroimaging has the potential to improve our understanding of the neural correlates of depression after TBI and may improve our capacity to accurately predict and effectively treat this condition. We conducted a systematic review of structural and functional neuroimaging studies that examined the association between depression after TBI and neuroimaging measures. Electronic searches were conducted in four databases and were complemented by manual searches. In total, 2035 citations were identified and, ultimately, 38 articles were included, totaling 1793 individuals (median [25-75%] sample size of 38.5 [21.8-54.3] individuals). The most frequently used modality was structural magnetic resonance imaging (MRI) (n = 17, 45%), followed by diffusion tensor imaging (n = 11, 29%), resting-state functional MRI (n = 10, 26%), task-based functional MRI (n = 4, 8%), and positron emission tomography (n = 2, 4%). Most studies (n = 27, 71%) were cross-sectional. Overall, depression after TBI was associated with lower gray matter measures (volume, thickness, and/or density) and greater white matter damage. However, identification of specific brain areas was somewhat inconsistent. Findings that were replicated in more than one study included reduced gray matter in the rostral anterior cingulate cortex, pre-frontal cortex, and hippocampus, and damage in five white matter tracts (cingulum, internal capsule, superior longitudinal fasciculi, and anterior and posterior corona radiata). This systematic review found that the available data did not converge on a clear neuroimaging biomarker for depression after TBI. However, there are promising targets that warrant further study.