Structural MRI sample acquisition and quality control: Structural MRI with high resolution T1-weighted images adequate for morphometry was available for 204 patients with recurrent unipolar depression and 186 control subjects. MRI was acquired at the MPI of Psychiatry in the context of the acquisition of the Munich recurrent unipolar depression replication samples. A detailed description of study participant selection and image processing is available in the supplemental method section. Automated regional volumetry: In brief, image preprocessing was performed as for voxel based morphometry to gain grey matter (GM) maps with preserved local volume in stereotactic space. Histologically validated cytoarchitectonic probability maps (Amunts et al., 2005) were used to create regional volumetry masks for the left and right hippocampus and subregions cornu ammonis (CA: CA1–3), subiculum (SUB) and dentate gyrus (DG). The sum of all modulated GM voxels within the regional masks was calculated using in-house software programmed in IDL (http://www.creaso.com). Statistical analysis: Analysis of covariance (ANCOVA) was performed for left and right total hippocampal GM volume and each three subregions with two-level factors group (patients, controls), genotype (rs1545843 AA vs.
