Electroconvulsive therapy induces rapid microstructural and macrostructural changes, but microstructural changes are longer-lasting

Background Electroconvulsive therapy (ECT) is an effective treatment for major depressive episodes, though its mechanisms remain unclear. Its use is limited due to stigma and possible cognitive side-effects. Repeated magnetic resonance imaging (MRI) could provide further insights into the brain changes associated with ECT’s efficacy and cognitive outcomes. Methods We analyzed prospective longitudinal repeated MRI, cognitive, and efficacy data of depressed ECT-patients. Structural and diffusion tensor imaging (DTI) MRI scans were conducted at baseline, directly after initial ECT-sessions, within two weeks after the course and at three months follow-up. Test-retest effects were controlled by including 26 matched healthy controls ( n =26). Linear and nonlinear changes in grey matter (GM) volume, white matter (WM) volume, mean diffusivity (MD) and fractional anisotropy (FA) were assessed. Early brain changes were associated with cognitive and efficacy outcomes. Results After the 3 ^rd ECT-session ( n =19), subcortical GM volumes increased, accompanied by right lateralized decrease of MD in those areas. Two weeks post-ECT ( n =30), cortical GM volume increased which returned to baseline after three months. In WM, MD linearly increased post-ECT, without widespread FA changes, and MD did not return to baseline after three months ( n =30). ECT decreased verbal learning transiently, letter fluency, and animal category fluency tests ( n =23, p _bonferroni = 0.04; n= 22, p _bonferroni = 0.04; n= 62, p _bonferroni = 0.02). Early brain changes were not associated with cognitive performance or efficacy. Conclusions These results suggest that ECT induces rapid changes in brain microstructure and macrostructure. But while macroscopic increases are temporary, microscopic changes in brain structure are longer-lasting.