Data were from the PROSPER cohort sequential prevention trial, which included students across 28 school districts in Iowa and Pennsylvania. Half of the districts were randomly assigned to receive preventive interventions targeting adolescent substance use, yielding 14 intervention communities and 14 control communities. Students in all 28 school districts were invited to complete in-school surveys, and 90% participated. Two cohorts of students participated. Pre-intervention assessments were conducted in school during the fall semesters of 2002 and 2003 for cohorts 1 and 2, respectively (first semester of 6th grade). Follow-up in-school surveys were given annually from 0.5 years to 6.5 years past baseline (from spring semester of 6th grade to spring semester of 12th grade). Additionally, a random sample of 2,267 families of youth in Cohort 2 of the PROSPER project were invited to participate in the in-home data collections, which consisted of interviews and parent and adolescent questionnaires in Waves 1 through 5; 979 (43%) participated.
