PCSK9 and major depressive disorder: In the univariate analysis the severity of depression (BDI-II score) was positively associated with PCSK9 circulating levels with a rise of 0.44% (β = 2.75, Table 3) for every one-unit increase of BDI-II (Δ % = 0.44, 95%CI 0.23–0.65, p < 0.0001).