as the onset age for SI and SA was fairly low and typically preceded the onset of substance use and dependence. That is, in many instances, the typical age of onset of substance use and dependence occurred after the onset of SI and SA. Despite this, caution is needed in deriving any causal inference, as recall bias and other unmeasured confounders may be responsible for observed patterns of results. Fifth, due to their low prevalence, particularly at earlier ages, we did not examine illicit drugs other than cannabis. Sixth, when examining early use and dependence, never users were treated the same as late and non-dependent users (i.e., coded as “0”) respectively. This creates a confound, in that associations that are specific to early onset of use or onset of dependence cannot be disentangled for associations with onset of any use. Future studies should study substance involvement as a multi-stage process. Seventh, despite the longitudinal design, we did not study whether substance involvement was associated with new onsets of SI and SA, nor do we have data to examine completed suicides. Such an analysis will be more feasible when greater numbers of participants complete further follow-up assessments. Similarly, we did not
