A conditional growth model with sons’ externalizing status added as a predictor of intercept and slope was fit.4 As before, P300 decreased significantly with age, F(1, 571) = 86.08, p < .001. Once the externalizing disorder status of the sons was added to the model, there was only a trend for the trajectories of the paternal AAB group to differ from the paternal low-risk group, χ2(1, N = 243) = 3.31, p= .069. The developmental trajectories of young men who developed an externalizing or early-onset substance disorder differed significantly from those who did not, χ2(1, N = 369) = 12.20, p < .001. The trajectory for the men with a disorder had a smaller intercept (M = 21.39 µV, SE = 1.03) than that of the men who did not develop a disorder (M = 24.33 µV, SE = 0.90), F(1, 41) = 10.94, p = .002, although the difference in slope between the groups was relatively small (mean difference = −.063, SE = .135), F(1, 571) = 0.22, p = .640.
