Substance use and variation in sexual partnership rates among young MSM and young transgender women: Disaggregating between and within-person associations

Background: Substance use has been extensively linked to sexual behavior and HIV/STI risk among men who have sex with men (MSM) and transgender women (TW). However, the impact of specific substances and on specific partnership types is not well characterized. The current study seeks to estimate the association between specific substances and partnership rates while carefully disaggregating between and within-person associations to characterize the nature of these associations and inform prevention interventions. Methods: Using data from a longitudinal cohort (n = 1159) of young MSM (YMSM) and young TW (YTW), we utilized a series of hybrid mixed effect models to estimate the associations between substance use (i.e., heavy episodic drinking [HED], marijuana, cocaine, ecstasy, methamphetamine, poppers, prescription stimulant, prescription painkiller, and prescription depressants) and partnerships (i.e., one-time, casual, and main). Results: Results from multivariable models indicated people using substances had higher one-time (HED, poppers) and casual (HED, methamphetamine, poppers) partnership rates. In addition, participants reported higher rates of one-time (HED, ecstasy, methamphetamine, poppers) and casual partners (HED, marijuana, cocaine, methamphetamines, poppers) during periods of substance use. Conclusion: These findings confirm that the highest rates of sexual activity occur among YMSM-YTW using substances during periods of substance use. Yet, these findings should caution researchers against simplistic generalizations as these associations differ across substance and partnership types. Efforts to promote the health of MSM-YTW who use substances should carefully consider this complexity as interventions accounting for the unique cultural context of substance use in these populations are most likely to be successful.