The micro-social risk environment for injection drug use: An event specific analysis of dyadic, situational, and network predictors of injection risk behavior

Background: This study explores the risk environment for drug use by examining injection risk behavior during specific injection episodes. By leveraging multiple observations of injection episodes of participants, the study attempts to move beyond global assessment of environmental variables to simultaneously model within (i.e., event level) as well as between (i.e., individual level) predictors of injection risk. Furthermore, gender is also explored as a potential moderator of the relationship between the association of specific partner characteristics (e.g., having an injection partner who is also a sexual partner) and injection risk behavior. Methods: Data is used from the Sexual Acquisition of Transmission of HIV Cooperative Agreement Study (SATHCAP). Multilevel structural equation modeling is utilized to predict within and between variations in underlying injection risk behavior as measured using four indicators of injection risk. Results: Results indicated that a number of partner level characteristics (i.e., being emotionally close with the partner, sexual partnership, being a first time partner) and one social situational (i.e., the number of non-injectors present at the injection episode) characteristic predicted event level injection risk behavior. However, the impact of partner characteristics also appears to be moderated by gender of the participants. More specifically, sharing a sexual partnership with an injection partner was more strongly associated with injection risk among females as compared to males and females indicated higher levels of risk when injecting with other females while the partner's gender showed no significant association with risk for male injectors. Conclusion: These results suggest that people who inject drug do report varying levels of risk during different injection episodes and this variation can be explained by partner and situational characteristics. Improved understanding of the social processes surrounding injection episodes is required to further refine harm reduction approaches.