HAMP and major depressive disorder: The more the symptoms were improved, the lower the hepcidin levels were, independent of inflammation, age, sex, sleep disturbance (e.g., sleep quality, daytime sleepiness, insomnia severity) and mood status (e.g., depression, anxiety), 12 weeks after treatment (β = 0.002, 95% CI 0.00–0.00, p = 0.005).