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No Changes in Gray Matter Density or Cortical Thickness in Late-Life Minor Depression.

To the Editor: Minor depression (MinD) is a subclinical depressive disorder affecting nearly 10% of the elderly population.1 According to the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), a minor depressive episode requires 2 to 4 depressive symptoms that are present for at least 2 weeks. Minor depressive disorder is diagnosed when a lifetime history of major depressive disorder (MDD) is excluded.2 Although MinD may seem transient, its consequences are often severe.3,4 The pathophysiology of MinD remains largely unexplored.1 We analyzed structural magnetic resonance images (MRI) of 38 subjects with MinD and 80 healthy controls (aged 60–79 years) using voxel-based morphometry (VBM) and region-of-interest (ROI) analyses of gray matter density and cortical thickness. According to meta-analyses5–10 of structural brain changes in MDD, we hypothesized disease-specific decreases of gray matter density in the bilateral anterior cingulate cortex (ACC), hippocampus, and amygdalae and the right dorsomedial frontal cortex. In the ROI analysis, we expected decreased gray matter density within the meta-analytically derived11 mask (Supplementary eFigure 1) (the largest cluster: left insula, temporal pole, inferior frontal, superior temporal gyrus) and cortical thinning bilaterally in the medial orbitofrontal cortex, fusiform gyrus, insula, rostral anterior, and posterior cingulate cortex and unilaterally in the left middle temporal, right inferior temporal gyrus, and right caudal ACC.12