Characterizing the composition and multiplexity of social support and drug use networks among people who inject drugs in Baltimore, Maryland

Network ties of people who inject drugs can have overlapping roles, including concurrent social support and drug use relationships. Examining the composition and overlap of multiple networks, including the prevalence and correlates of multiplex ties, may inform network-based interventions. Between June 2022-August 2023, a cross-sectional sample of 584 participants from the AIDS Linked to the IntraVenous Experience (ALIVE) cohort of people with a history of injection drug use completed social support and drug use network inventories. We examined ego-level demographics, drug use behaviors, and network characteristics, as well as alter-level social support, co-drug use, and multiplexity. We performed logistic regressions clustered by egos to study associations between multiplexity and ego-level drug use behaviors. 266 participants with active drug use nominated 813 social support alters and 265 drug use alters, of which 133 were multiplex ties. To their egos, multiplex ties were less close than simple social support ties (mean score of perceived relationship closeness, 4.2 vs. 4.6), but closer than simple drug use ties (4.4 vs. 3.2). Among all social support alters, being a multiplex tie (vs. a simple social support tie) was associated with egos’ increased odds of opioid use (adj.OR = 2.19 [95%CI = 1.24–3.85]) and polysubstance use (adj.OR = 1.97 [1.20–3.24]); multiplex sexual partners were associated with egos’ increased odds of injection drug use (adj.OR = 2.03 [0.93–4.44]) while multiplex relatives were associated with lowered odds (adj.OR = 0.25 [0.08–0.81]). Relationship types within multiplex ties exhibited distinct interaction patterns with egos and unique associations with ego drug use behaviors. Leveraging the structural and functional diversity of these relationships may optimize the development of effective network-based interventions.