Cessation of Injecting and Preceding Drug Use Patterns Among a Prospective Cohort of Street-Involved Youth.

PURPOSE: Injection drug use is prevalent among street-involved youth, but patterns of cessation are poorly described. We identified drug use patterns preceding injection cessation among street-involved youth.

METHODS: From September 2005 to May 2015, we collected data from the At-Risk Youth Study, a prospective cohort of street-involved youth in Vancouver, Canada, and limited the sample to actively injecting youth. The primary outcome was cessation of injecting self-reported at semiannual follow-up visits. We used Cox regression to identify drug use patterns preceding cessation.

RESULTS: Among 383 youth, 65% were male, mean age was 22.3 (standard deviation, 2.5; range, 15-30) years, and 171 (45%) ceased injecting for 6 months or more (crude incidence density 22 per 100 person-years; 95% confidence interval [CI], 19-26). Youth who ceased were less likely to have injected daily (adjusted hazard ratio [AHR], .40; 95% CI, .28-.56), injected heroin (AHR, .40; 95% CI, .29-.56), or injected crystal methamphetamine (AHR, .43; 95% CI, .31-.59) before cessation. Noninjection heroin use was positively associated with injection cessation (AHR, 1.52; 95 CI, 1.12-2.08). Addiction treatment was not associated with cessation. At the time of cessation, 101 (59%) youth continued to use "hard" noninjection drugs such as heroin and crystal methamphetamine.

CONCLUSIONS: Periods of injection cessation were common but frequently accompanied by ongoing noninjection drug use. Findings indicate that trajectories of injection drug use among youth are complex and highlight the need to further explore relationships between ongoing noninjection drug use and injection cessation.