Compared to healthy controls (n = 32), bilateral hippocampal volume (left hemisphere = left column, right hemisphere = right column) was significantly smaller in the MDD group at baseline (T1; MDD, n = 43). Significant volumetric increases were observed after just two ECT sessions (T2; MDD, n = 36), and after four weeks of treatment (T3; MDD, n = 29) hippocampal volume was comparable in patients and controls. Controls were scanned twice (C1, C2) about four weeks apart and did not show volumetric changes over time. Image adapted from [29], with permission.