APOE and depressive symptom measurement: Individuals with severe ID experienced a greater change in Depression-Behavior over time than individuals with mild ID (b = 0.148, p = 0.02, 95% CI [0.035, 0.261]), and APOE4 allele carriers experienced lower Aggression scores over time than non-carriers (b = −0.07, p = 0.05, 95% CI [−0.138, −0.001]).