DRD4 and attention deficit-hyperactivity disorder: There were no significant interactions between the DRD4 genotypes and perceived parental rejection [χ2 (3) = 2.70, p = 0.44], overprotection [χ2 (3) = 1.05, p = 0.79], and emotional warmth [χ2 (3) = 1.80, p = 0.62] in predicting class membership in ADHD symptom trajectories.