For each annual follow-up, the TLFB will cover time since last assessment to ensure continuous coverage of substance use patterns over the longitudinal study. As noted above, once youth have access to mobile technology that they can use in a confidential environment (typically by age 12), a 6-month TLFB interview will be administered by research staff directly with the adolescent via web and/or phone. These data will facilitate generation of overall metrics of adolescent substance use for each endorsed category, total substance used (in standard units), number of binge drinking episodes, drinks per binge episode, age of first use, age of first regular use (how “regular” substance use is defined at each time point can be determined by each scientist/authors accessing the data by altering or creating their own TLFB scoring code, e.g., “regular use” can be defined as using every week, every day, etc. for various time periods such as the past 3, 6, 12 months), dose per occasion, and total number of co-use days (all substance combinations).
