To account for the change in externalizing problems over time, an unconditional growth model was fit with random intercepts and a linear random slope for time (a random intercepts and slopes model). The unconditional growth model was a better fitting model than the unconditional means model (χ2[3] = 1382.63, p < .001), suggesting that externalizing problems change over time. Moreover, the model with a random effect of time fit better than a model with a fixed effect of time (χ2[2] = 1300.16, p < .001), suggesting that trajectories of externalizing problems differed between individuals.
