“…First, the sampling methodology and enrollment criteria resulted in a sample primarily consisting of high-risk youth with extensive histories of homelessness, criminal justice involvement, mental health care, drug treatment, and polydrug use. This sample of high-risk youth should not be viewed as necessarily representative of ketamine injectors more broadly, but rather as a subgroup of the larger population of ketamine users (Degenhardt and Topp, 2003;Dillon et al, 2003;Jansen, 2001;Curran and Morgan, 2000;Dotson et al, 1995) and/or young injection drug users (Crofts et al, 1996;Fuller et al, 2001;Sherman et al, 2002;Roy et al, 2002;Miller et al, 2006). Second, while a majority of the injection events described during interviews occurred since 2002, some happened as far back as the early 1990s.…”