IL4 and treatment resistant depression: Pre-ECT, levels of glial fibrillary acidic protein (GFAP), S100 calcium-binding protein B (S100β), CD81, IL-1β, IL-4, IL-6, IL-10, IL-17, tumor necrosis factor-alpha (TNF-α), and inflammatory markers interferon γ (IFN-γ) were significantly higher in TRD patients than in controls.