The parents and youth are contacted between the baseline and year 1 follow-up assessment for a 6-month follow-up phone interview to capture new onsets of substance use (based on youth report only). Once youth have access to private personal mobile devices (typically around age 12), youth will be contacted directly to complete the on-line 6-month TLFB. See Table 1 for all measures in the baseline and year 1 substance use module. Additional measures (e.g., motives for substance use, cannabis and nicotine acute withdrawal symptoms) will likely be added starting at year 2 follow-up sessions.
