Those who had developed an externalizing or earlier onset substance disorder had significantly different trajectories from those who did not have such a disorder. To a large extent, diagnostic status of the offspring is confounded with risk in this sample. Almost 92% of the paternal AAB group and 76.4% of the intermediate-risk group had at least one earlier onset substance disorder or other externalizing disorder. There are several reasons why an interpretation of trajectory differences as reflecting a vulnerability contributing to these disorders rather than an effect of having a disorder is reasonable.
