APOB and depressive disorder: Further stepwise multivariate regression analysis showed that serum ApoB levels (ß = −27.42, t = −2.68, p = 0.01), education (ß = 1.83, t = 2.55, p = 0.01), and age of illness onset (ß = −1.33, t = −2.21, p = 0.03) independently contributed to delayed memory score, which together accounted for 23.3% of the variance in delayed memory score of depressive disorder.