When the regression predicting walking speed (TUG) at month 6 from depression group was rerun with adjustment for week 6 cortisol:DHEAS ratio, the association with depression group became non-significant, with evidence of significant mediation using the Sobel test, (p = 0.01), such that a higher cortisol:DHEAS ratio explained the relationship between depression group and longer TUG speed. Here, SULT2A1 is linked to major depressive disorder.