Analyzing different ions in patients with depression, the authors suggested that elevated serum copper levels may additionally induce inflammatory processes by reducing anti-inflammatory cytokines (interleukin-4 and 10), increasing proinflammatory cytokines (interleukin-1beta, 2, 6, and 8 and tumor necrosis factor-alpha (TNF-alpha)), which are also considered in the inflammatory hypothesis of psychotic and mood disorders. Here, TNF is linked to major depressive disorder.