Effects of race, neighborhood, and social network on age at initiation of injection drug use.

OBJECTIVES We investigated individual- and neighborhood-level factors associated with adolescent initiation of injection drug use. METHODS Injection drug users (IDUs) who had been injecting 2 to 5 years underwent HIV testing and completed a sociobehavioral risk survey. Modeling techniques accounting for intraneighborhood correlations were used in data analyses. RESULTS Adolescent-initiating IDUs were less likely than adult-initiating IDUs to report high-risk sex and injection behaviors and more likely to report high-risk networks. African American IDUs from neighborhoods with large percentages of minority residents and low adult educational levels were more likely to initiate injection during adolescence than White IDUs from neighborhoods with low percentages of minority residents and high adult education levels. CONCLUSIONS Racial segregation and neighborhood-level educational attainment must be considered when drawing inferences about age at initiation of injection drug use and related high-risk behaviors.