Fig. 1

Schematic diagram of the study sample and analyses. Between December 2014 to May 2016 and June 2018 to November 2018, 1128 people who use drugs in Vancouver, Canada had witnessed an overdose event. *The sample was further restricted by the exclusion of witnessed overdose events (n = 608) where the respondent did not call EMS, but EMS arrived at the scene or was not needed. For the primary cross-sectional analyses, we utilized the most recent observations only among the analytic sample (120 observations excluded) to identify factors associated with EMS-calling. For the secondary analyses, which involved an interrupted time series analysis, we utilized the full 660 observations of the analytic sample and divided the observations into pre- and post-enactment of the Good Samaritan Drug Overdose Act samples