“…After cannabis, youth consistently identify POs as the most commonly misused drug (Johnston, O’Malley, Bachman, & Schulenberg, 2012) and the 2013 US Centre for Disease Control national survey of American high schools found that over 20% of grade 12 students have misused prescription drugs (Kann et al, 2014). In addition to concerns regarding increased risk of morbidity and mortality associated with PO use (Frank et al, 2015, Hall et al, 2008, Office of the National Drug Control Strategy, 2011, Okie, 2010, USCDCP, 2011, USCDCP, 2012, Roy et al, 2004, Silva et al, 2013, Warner et al, 2011 and Zosel et al, 2013), there are also signals from qualitative, retrospective and cross-sectional studies that PO use may facilitate transitions to injection drug use; however, the impact of PO misuse on the incidence of initiation into injecting has not been characterized (Lankenau et al, 2012, Mars et al, 2014, Peavy et al, 2012, Rigg and Murphy, 2013, Young et al, 2012 and Young and Havens, 2012). The objective of this longitudinal study was to examine the relationship between PO misuse and time to injection initiation within an open prospective cohort of street-involved youth in Vancouver, Canada.…”