CXCL8 and Menkes disease: Patients with MD displayed heightened levels of pro-inflammatory cytokines, such as IL-6, IL-8, and tumor necrosis factor-α (TNF-α), while reduced levels of anti-inflammatory cytokines, such as transforming growth factor-β1 (TGF-β1), along with an increase in TNF-α levels were observed in the plasma of depressed patients (Caraci et al., 2018), which may significantly contribute to treatment resistance in MD.