We found that reduced CSF PCSK9 levels were not significantly associated with MDD (relaxed-PSMR-multi = 0.816, stringent-PSMR-multi = 0.600), and mood instability (relaxed-PSMR-multi = 0.022, stringent-PSMR-multi = 0.014) in either the relaxed or stringent set (Fig 2, Table 1, data in S3 Table). This evidence concerns the gene PCSK9 and major depressive disorder.