SNCA and major depressive disorder: Depression scores demonstrated no correlation between the continuous values of α-synuclein and GDS scores (p = 0.53), Aβ-42 (p = 0.29), pTau (p = 0.60), or tTau (p = 0.66), as well as in biomarkers between patients with GDS ≥ 5 and GDS < 5 (Table 7, Figure 2), both when analyzing continuous biomarker levels and dichotomized levels and ratios.