Cognitive impairment and depression: Meta-analysis of structural magnetic resonance imaging studies

Abstract

Longitudinal comorbidity of depression and cognitive impairment has been reported by number of epidemiological studies but the underlying mechanisms explaining the link between affective problems and cognitive decline are not very well understood. Imaging studies have typically investigated patients with major depressive disorder (MDD) and mild cognitive impairment (MCI) separately and thus have not identified a structural brain signature common to these conditions that may illuminate potentially targetable shared biological mechanisms. We performed a meta-analysis of. 48 voxel-based morphometry (VBM) studies of individuals with MDD, MCI, and age-matched controls and demonstrated that MDD and MCI patients had shared volumetric reductions in a number of regions including the insula, superior temporal gyrus (STG), inferior frontal gyrus, amygdala, hippocampus, and thalamus. We suggest that the shared volumetric reductions in the insula and STG might reflect communication deficits and infrequent participation in mentally or socially stimulating activities, which have been described as risk factors for both MCI and MDD. We also suggest that the disease-specific structural changes might reflect the disease-specific symptoms such as poor integration of emotional information, feelings of helplessness and worthlessness, and anhedonia in MDD. These findings could contribute to better understanding of the origins of MDD-MCI comorbidity and facilitate development of early interventions.

Keywords: Major depressive disorder; Meta-analysis; Mild cognitive impairment; Shared volumetric reductions; structural magnetic resonance imaging (MRI); voxel-based morphometry (VBM).

Fig. 1

PRISMA flow diagram representing selection procedure in meta-analysis

Fig. 2

Regions of GM volume decreases underlying MDD and MCI symptomatology. Shared regions are depicted in green, MDD-specific regions in blue, and MCI-specific regions in yellow. (R: right; L: left; HC: healthy controls; MCI: mild cognitive impairment; MDD: major depressive disorder; g: gyrus; Voxel-wise threshold p < 0.005 uncorrected; minimum cluster extent 10 voxels, except for multimodal meta-analysis (p < 0.0025))