IL6 and major depressive disorder: Data extracted included study design, sample size, dosages, biomarkers (e.g., cortisol, interleukin-6 (IL-6)), clinical outcomes [the Perceived Stress Scale-10 items (PSS-10), the State–Trait Anxiety Inventory (STAI), the Computer Vision Syndrome Questionnaire (CVS-Q), the Pittsburgh Sleep Quality Index (PSQI), and the Hospital Anxiety and Depression Scale (HADS)], and statistical significance (p < 0.05). A qualitative synthesis was conducted, focusing on the synergistic effects of components.