At initial recruitment, an information packet was mailed to eligible students at participating high schools. Subsequently, participants were re-recruited through school or contact information they provided. At each wave, participants (and their legal guardians during adolescence) completed informed consent. At waves 1-4, youth completed surveys in a group administration format at school, and their primary caregivers provided information via mail surveys and phone interviews. In waves 5-7, trained interviewers conducted individual interviews with the participants in the participants' homes or at a research site. Sensitive questions, including those on substance use and friends' alcohol use, were answered privately using a self-interview format. For the genetic supplement, participants were mailed a saliva collection kit (DNA Oragene); they returned the sample to the research team by mail. Participants were compensated for their time at each assessment.
