Because several studies have reported a systemic inflammatory state in patients with SUD and common psychiatric disorders such as MDD, we explored whether circulating concentrations of G-CSF in the plasma were altered in patients with SUD (CUD and AUD) and psychiatric comorbidity from outpatient treatment programs, as well as in patients with MDD but not SUD from primary-care settings in Spain. Here, CSF3 is linked to major depressive disorder.