We selected three substances (alcohol, marijuana, and cocaine) for analysis because they represent a range of availability, severity, and legal statuses, and both the MTFS and SAGE studies assessed these substances in the same manner. For each substance, both studies assessed ever use of the substance and endorsement of each of the seven DSM-IV dependence criteria (in SAGE, via the SSAGA-II [33,34]; and in the MTFS, via the CIDI-SAM [35]). For the MTFS, lifetime ever use and dependence symptom endorsement was established by aggregating across all longitudinal assessments through the age 25 assessment. That is, ever use or any substance dependence symptom was considered “present” if the participant met the criterion at any assessment. Although not pathological, we include the ever use criterion to differentiate individuals exposed to a substance who have no dependence symptoms from those who were never exposed. Substance abuse symptoms were not included in the present analyses, as equivalent abuse criteria were not assessed in both the SAGE and MTFS samples.
