Abstract
Injection drug use (IDU) is of increasing public health concern in the United States. Misuse of and addiction to opioids has contributed to declining life expectancies and rebounding risk of HIV and HCV acquisition among people who inject drugs. While some effective treatment strategies for individuals with substance use disorders have been established, effective interventions to prevent IDU require greater tailoring to subpopulations and social contexts. To better understand contextual variables associated with initiation of IDU, we conducted a narrative review of the existing literature that assessed correlates of age of first injection. We found sixteen studies that met our inclusion criteria. Across studies, later IDU initiation was associated with being African American and female, while early initiation was associated with earlier illicit substance use, childhood trauma, and incarceration. We also found that early initiation was associated with riskier substance-using behaviors, though the findings were mixed with respect to differences between early and late initiates in infectious disease prevalence. These correlates of age of first injection can potentially inform tailored injection prevention strategies. By identifying the features and behaviors of relevant subpopulations before they inject, interventions to prevent IDU could become more effective.