Regular MDMA use is associated with decreased risk of drug injection among street-involved youth who use illicit drugs

Objectives: Childhood trauma is common among street-involved youth and is associated with injection drug use. Illicit 3,4-Methylenedioxymethamphetamine (MDMA) use is also common among street-involved youth, and data suggest this substance has clinical utility in management of post-traumatic stress disorder (PTSD) and associated harms. Despite this, little is known about co-occurring patterns of MDMA use and injection drug use. Methods: Data were derived from a prospective cohort of street-involved youth using illicit drugs in Vancouver, Canada. Using multivariable generalized estimating equation logistic regression, we examined the association between MDMA use and the use of injection drugs, adjusting for confounders such as polysubstance use and sociodemographic factors. Results: 4941 surveys from 1208 participants between September 2005 and May 2015 were included. Of these, 829 (68.6%) were male, 815 (67.5%) reported white ethnicity, and median age was 21.7 years. Overall, 599 (49.6%) participants reported MDMA use, 544 (45.0%) reported injection drug use, and 244 (20.2%) reported concurrent MDMA and injection drug use at least once during the study period. In multivariable analyses, regular MDMA use was significantly negatively associated with injection drug use (Adjusted Odds Ratio [AOR] = 0.57, 95% CI: 0.46–0.69). Discussion: After accounting for socio-demographic factors and polysubstance use, periods of reported regular MDMA use were negatively associated with reported injection drug use among this cohort. These findings suggest that, unlike the use of most other non-injection drugs, illicit MDMA use does not appear to promote injection drug use but rather is associated with a reduced likelihood of injection drug use.