Comorbidity Survey – Replication (18%; (Kessler et al., 2004)). Even though we control for family history, and it exerts significant effect, it is possible that our study design influenced the pattern of our results. It is also noteworthy that rates of cigarette smoking exceed those of cannabis use in this sample, however, this observation is consistent with estimates from the recent Monitoring the Future Survey (Johnston et al., 2016). Second, even though the study was designed to be longitudinal, it is ongoing, and not all participants have had the opportunity to participate in later follow-ups. Thus, younger participants may have had fewer opportunities to report their substance use behavior and may not have passed the age of risk for onset of cannabis use or of developing substance dependence. To leverage this study design, we employed survival models which allowed for such right censored data and we included age at last interview as a covariate. A related concern is attrition – as the study is ongoing, non-participation in subsequent waves is not necessarily indicative of attrition. However, analyses of those who were eligible to have participated in the 6 year follow-up found no significant differences related to substance use behaviors or
