TGFB1 and depressive symptom measurement: Regarding associations among the core biomarkers and depression severity, GDF11 was negatively correlated with GDF15 (r=-0.643, p<0.01) and HAMD-17 scores (r=-0.663, p<0.01), while showing a positive correlation with TGF-β1 (r=0.493, p<0.01).