In multivariable analysis, injection heroin use (Adjusted Hazard Ratio [AHR] 6.11; 95%CI 3.24-11.52), having an intimate partner who injects drugs (AHR 2.93; 95%CI 1.57-5.46), workplace violence (AHR 2.85; 95%CI 1.74-4.67), HIV seropositivity (AHR 2.69; 95%CI 1.45-5.00), and childhood abuse (AHR 1.86; 95%CI 0.99-3.49) were independently associated with initiating CM injection.