IL3 and major depressive disorder: Xiu et al. (2015) found that higher IL-3 serum levels are associated with more severe symptoms in patients with schizophrenia (Xiu et al., 2015), and Al-Hakeim et al. (2015) found higher levels of inflammatory markers in schizophrenia than in MDD patients and healthy controls. These findings, if confirmed, might suggest the use of anti-inflammatory medications as add-on therapy in psychotic disorders (Zarate, 2023).