Abstract
The present study aims to replicate previously reported grey matter volume (GMV) differences between currently depressed patients with bipolar I disorder, patients with unipolar depressive disorder, and healthy control (HC) participants using voxel-based morphometry. In this replication, the terms Unipolar Depressive Disorder (UD) and Bipolar I Depressive Disorder (BP1) from the original study correspond to our groups Major Depressive Disorder (MDD) and Bipolar Disorder (BD), respectively. Specifically, the present study focuses on the key finding reported by Cai et al. (2015), namely reduced GMV in the right middle cingulate gyrus in patients with BP1 compared to both healthy controls and patients with UD. Furthermore, GMV in the right middle cingulate gyrus was negatively associated with depression severity as measured by the Hamilton Depression Rating Scale. In addition, the authors reported reduced GMV in the right inferior frontal gyrus in both patient groups relative to healthy controls, which will be treated as a secondary finding of the original study rather than the primary replication target.