Geospatial and Environmental Predictors of Momentary Substance Use in a Sample of Young Adults Experiencing Homelessness

Background and Purpose:Young adults experiencing homelessness are known to have high rates of trauma and victimization, in addition to leading socially complex and chaotic lives. Further, higher rates of substance use are documented among young adults experiencing homelessness. As a result, housing programs have been implemented in this population. However, little is known about the impact of such programs on substance use behaviors. The purpose of this study was to use geological ecological momentary assessment (GEMA) to examine context of substance use behavior and the effects of housing programs on substance use throughout the day.

Methods: Housed (n= 132) and unhoused (n=85) participants, ages 18-29 years old, were recruited from a variety of housing programs and recruitment sites as part of a study examining HIV risk environment for young adults in supportive housing. Participants were provided smartphones for one week and prompted with up to eight surveys per day that queried momentary drug use behavior, among other variables (e.g., stress, affect). Location data (GPS) were collected from onboard sensors each minute and variables were generated to determine proximity to the housing program or typical place of sleep. Hard drug, marijuana, and alcohol use were entered as outcomes in multilevel models to test for effects of geospatial proximity and examine differences between housed and unhoused participants.

Results: Compared to those in housing, unhoused participants were 3.27 times as likely (95% CI: 1.56-6.85) to report using alcohol and 3.46 times as likely (95% CI: 1.53-7.80) to report using marijuana at any given two-hour period throughout the day (p’s < 0.01). Similarly, unhoused participants tended to report more hard-drug use and temptation to use drugs than unhoused participants at each two-hour period, although the relationship was only marginally significant (p’s < 0.10). Among those that were housed, participants that were near their housing program were 62% more likely (95% CI: 1.09-2.41) to report using marijuana than when they were away from their home.

Conclusions and Implications: As anticipated, participants in housing were less likely to use alcohol throughout the day. Similarly, formerly homeless young adults used marijuana near their housing program, even though they reported less marijuana use overall. The findings suggest that housing programs may result in reduced substance use, even if housing provides a more convenient location for substance use. However, the study may be limited by the selection process for housing programs, and thus effects may reflect differences between young adults that qualified for supportive housing and those that did not. Future longitudinal research on the effects of transitioning from homelessness could elucidate within-person change as a result of entering a housing program. Implications include a continued need for more substance abuse services in housing programs to support formerly homeless youth.