APOE and major depressive disorder: Compared to PiB(−) aMCI patients, PiB(+) aMCI patients had lower scores in the Geriatric Depression Scale, a higher proportion of APOE4 carriers, and a lower proportion of diabetes mellitus [one PiB(+) aMCI (3.2%) vs. 4 PiB(−) aMCI (25.0%) patients, P = 0.040 for chi-square test] and hypertension [10 PiB(+) aMCI (32.3%) vs. 10 PiB(−) aMCI (62.5%) patients, P = 0.047].