PCSK9 and major depressive disorder: We found no association between PCSK9 reduced levels, and MDD (relaxed-PSMR = 0.190, stringent-PSMR = 0.106) and mood instability (relaxed-PSMR-multi = 0.012, stringent-PSMR-multi = 0.090) in either the relaxed or stringent set.