Informed consent was obtained before the start of every interview. Participants were given a description of the study, read a statement describing the legislation regarding the confidentiality of any information provided by participants, and assured that participation in the study was voluntary. Additional information on data confidentiality maintenance is available elsewhere (SAMHSA 2003, 2013). Surveys were administered by computer-assisted personal interviewing (CAPI) conducted by an interviewer and audio computer-assisted self-interviewing (ACASI). Use of ACASI was designed to provide respondents with a private and confidential means of responding to questions, and to increase honest reporting of illegal drug use and other sensitive behaviors (SAMHSA, 2003, 2013). Respondents were offered U.S. $30 for participation. The analyses were based on de-identified publicly available data exempt from Institutional Review Board review.
