APP, MAPT, APOE, and other variants in pathogenic genes (Table 1) as well as the presence of schizophrenia- and/or depression-related SNPs [25,26,27], together with additional metabolic disorders [28], cerebrovascular risk or consolidated vascular damage [4,29,30,31], premorbid personality [32], and inappropriate management may contribute to BDs in AD. Here, APOE is linked to major depressive disorder.